JP2005231239A - Molding method, injection molding machine, injection compression molding machine, mold, optical disk original board, and optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a molded article having a good shape quality by preventing the molded article from being deformed by a pressure change of a material resin filled into a cavity and achieving a mechanism directly working on the pressure change without complication of the employed mold. <P>SOLUTION: A convex slide cavity wall 17 is formed in a fixed mold 1 to make the cavity 3 a closed space during moving a movable mold 2. The thickness of the cavity is broadened by a mold opening amount 12 from a predetermined thickness 15 using a mold clamping mechanism, and a predetermined amount of the material resin 4 is injected and filled while keeping the stopping state. The cavity forming portion of the movable mold 2 is advanced by a compressing amount 16 decided by the predetermined cavity thickness 15 to a position where the cavity thickness becomes thin to compress the material resin 4 injected and filled into the cavity 3. The material resin 4 is cooled and solidified in the cavity 3. Then the molded article 8 is taken out by retreating the movable mold 2 and opening the cavity 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is a molding in which a molten material resin is injected and filled in a cavity of a predetermined shape formed between a fixed mold and a movable mold, and the material resin is cooled and solidified in the cavity and then taken out of the mold. The present invention relates to a method, an injection molding apparatus, an injection compression molding apparatus, and a molding die, and more particularly, to an optical disk master as a molded product that requires high shape accuracy and precise pattern fine transfer, and further to an optical disk as a product.

  An injection molding technique in which a melted material resin is injected and filled in a cavity of a predetermined shape formed between a fixed mold and a movable mold, and the material resin is cooled and solidified in the cavity and then taken out of the mold. This technology has extremely advantageous features as a technology for producing molded parts that are parts or products of the same shape in large quantities and at low cost.

  In recent years, for example, optical parts and elements such as lenses used in laser printers, and parts or products that require precise shape quality such as high-density optical disk substrates are also molded and produced by injection molding. Many attempts have been made to utilize the mass productivity and cost advantages of molding.

  FIG. 4 is a process diagram showing an injection molding process. First, the fixed mold 1 is closed by the movable mold 2 to form a cavity 3 having a predetermined shape (FIG. 4A), and the molten material resin 4 is injected and filled into the cavity 3 (FIG. 4B). When the material resin 4 is injected and filled in the entire cavity 3, a pressure 6 is generated in the material resin 4 in the cavity 3 by the injection pressure 5 for injection filling the material resin 4 (FIG. 4C). At this time, a predetermined mold clamping force 7 is applied to the movable mold 2 in advance by a mold clamping mechanism (not shown) of the molding apparatus, and the cavity 3 is maintained in the initially formed shape. Therefore, the pressure 6 functions to deform the material resin 4 so as to follow the shape of the cavity 3 so as to adhere to the inner wall of the cavity 3 and make the shape of the material resin 4 the same as the shape of the cavity. Subsequently, after the material resin 4 is cooled and solidified in the cavity 3 (FIG. 4D), the movable mold 2 is retracted to open the cavity 3, and the molded product 8 is taken out (FIG. 4E).

  Incidentally, the pressure 6 is one of the factors in the molding process that plays an important role in obtaining the above-mentioned molded product having a precise shape quality, in other words, a molded product having a shape in which the cavity shape is precisely transferred. The greater the pressure 6, the stronger the force that the material resin 4 deforms following the shape of the cavity 3. Therefore, when molding optical parts / elements and high-density optical disk substrates that require good shape quality by precisely transferring the shape of the cavity 3, a device for generating a larger pressure 6, such as large clamping It is customary to apply force 7 or the like.

  As a method for generating the pressure 6 more effectively, there is an injection compression molding method. FIG. 5 is a process diagram showing main processes of the injection compression molding process. In addition, the same number is attached | subjected about the component similar to FIG.

  A movable core 2 is provided with a compression core 9 that can move. The compression core 9 includes a shape that is a part of the cavity 3. At the time of molding, first, the compression core 9 is retracted by a predetermined compression margin 10 and the material resin 4 is injected and filled in a state where the thickness of the cavity 3 is increased (FIG. 5A), and a predetermined amount of material is injected. At the timing when the resin 4 is filled in the cavity 3, a compression mechanism (not shown) of the molding apparatus is operated to advance the compression core 9, and a predetermined compression force 11 is applied to the material resin 4 filled in the cavity 3. It adds (FIG.5 (b)). The compression force 11 generates a pressure 6 on the material resin 4 in the cavity 3.

  As described above, in the injection compression molding method, since the operation of generating the pressure 6 on the material resin 4 directly by the compression mechanism of the molding apparatus is performed, the pressure 6 can be generated more accurately and accurately. Become. Further, in this injection compression molding method, the operation of injecting and filling the material resin 4 into the cavity 3 is performed in a state where the thickness of the cavity 3 is expanded by 10 to the extent that the molded product having the same cavity thickness is molded by the injection molding method. Compared to the above, it is possible to perform the injection filling operation with a lower flow resistance, and the internal distortion of the obtained molded product can be reduced.

  As a molding method for obtaining the same effect as the above-described injection compression molding method, there is a pseudo compression molding method using mold opening control during the injection process. In this molding method, as shown in FIG. 6, the material resin 4 is injected and filled in a state where the movable mold 2 is stopped at a position where the cavity 3 is opened by a predetermined mold opening amount 12 (FIG. 6A). The mold clamping mechanism (not shown) of the molding apparatus is operated at a timing when a predetermined amount of the material resin 4 is filled in the cavity 3 to advance the movable mold 2, and the material resin 4 filled in the cavity 3 is predetermined. The mold clamping force 7 is applied (FIG. 6B). The mold clamping force 7 generates a pressure 6 on the material resin 4 in the cavity 3.

  In this pseudo compression molding method, since the pressure 6 is directly generated on the material resin 4 by the mold clamping mechanism of the molding apparatus, the injection filling operation is performed in a mold open state in which the cavity thickness is increased. The same effects as those of the injection compression molding method can be obtained with respect to the flow state of the resin. Further, in this pseudo compression molding method, an essential compression core structure is not necessary for a mold used for injection compression molding, and a normal injection mold having a relatively simple structure can be used. Therefore, not only has it become difficult to inject and fill the material resin into the cavity because the plate thickness is reduced compared to the CD-based optical disc, but more precise pits and guide grooves are transferred more accurately, This pseudo compression molding method is widely used for DVD systems that require better quality in terms of shape quality such as warpage and waviness, and for optical disk substrate molding used for high-density optical disks higher than DVD.

  The pressure generated in the material resin injected and filled in the cavity as described above plays an important role in transferring the cavity shape to the material resin, and finally to the molded product. However, it is not always possible to obtain a molded product with good shape quality if a large pressure is simply generated in the material resin.

  For example, when the cooling process is completed and a molded product is taken out of the cavity while a large pressure is still generated in the material resin, the molded product is reshaped to relieve the pressure remaining at the time of removal. As a result, a molded product with good shape quality cannot be obtained. Therefore, in order to obtain a molded product with good shape quality, pressure is generated on the material resin injected and filled in the cavity to transfer the cavity shape, and then the generated pressure is taken out of the cavity. It is necessary to reduce it to a level where the product does not deform.

  One method of reducing the pressure generated in the material resin is an operation of cooling the resin injected and filled in the cavity. The material resin is heated by a molding device and injected and filled into the cavity in a molten state at a high temperature. At the same time, it fills the cavity and conducts its own heat to the mold to lower the temperature and lower the temperature. Along with this, the material resin starts to shrink. In other words, it can be said that the shrinkage phenomenon of the material resin accompanying the temperature decrease is that the material resin is brought into close contact with the inner wall of the cavity and the pressing force, that is, the pressure is decreased as the temperature is decreased.

  In the usual injection molding method or injection compression molding method, the material resin is cooled in the cooling step after the material resin is injected and filled into the cavity, and the temperature is lowered to solidify the molten material resin, and at the same time the pressure is reduced. The operation is performed. Then, as the temperature is lowered, the material resin is sufficiently solidified and the pressure is lowered to a level at which the shape of the molded product is not deformed, and then taken out of the cavity.

  However, it is very difficult to uniformly control and lower the temperature of the material resin injected and filled in the cavity, in other words, to uniformly control and lower the pressure. As a result, when the temperature of the material resin becomes non-uniform, that is, the pressure becomes non-uniform, the molded product taken out of the cavity is deformed by the stress generated inside the molded product due to the non-uniform pressure. . In addition, depending on the shape of the molded product, temperature or pressure non-uniformity is extremely generated in a part of the material resin in the cavity, and the resin resin partially releases from the cavity inner wall during the cooling process. "Is more likely to occur.

  Therefore, in Patent Document 4, “sink” is prevented by adding a “sink prevention mechanism” to a portion corresponding to a cavity where a “sink” is likely to occur depending on the shape of the molded product. Japanese Patent Application Laid-Open No. H10-228867 proposes a device for improving the shape accuracy of a desired portion of a molded product by trying to obtain it, or conversely causing intentional “sink” in a part of the molded product. However, in these methods, it is necessary to give a complicated mechanism to the mold to be used and to control the complicated mechanism very strictly, and the mass productivity and cost advantage of injection molding are impaired.

As a method for reducing the pressure of the material resin injected and filled in the cavity by a mold clamping mechanism or a compression mechanism for generating the pressure, there are techniques described in Patent Documents 1 and 2.
JP 2003-170480 A JP-A-8-11178 Japanese Patent Laid-Open No. 4-112024 JP 2001-293758 A JP-A-11-28745

  The molding methods described in Patent Documents 1 and 2 are methods in which the clamping force or compression force applied to generate pressure on the material resin injected and filled in the cavity is changed slightly during the cooling process, and the gold used This is advantageous in comparison with those described in Patent Documents 4 and 5 in that it is not necessary to give a special mechanism to the mold. However, these methods for controlling the clamping force or compression force also have the following problems.

  For example, before performing the operation of reducing the mold clamping force or compression force during the cooling process, these methods also apply a predetermined mold clamping force or compression force to the material resin injected and filled in the cavity. This is done to obtain a molded product with the cavity shape transferred. Then, at the stage where the large mold clamping force or compression force is applied, as shown in FIG. 7A, in the injection molding method, the movable mold 2 abuts the fixed mold 1 and the parting surface 13, and FIG. As shown in (b), in the injection compression molding method, the shape of the cavity 3 becomes a “predetermined shape” by advancing the compression core 9 to the forward limit position 14. Further, during the subsequent cooling step, the state of receiving the mold clamping force 7 or the compression force 11 having a certain size at the parting surface 13 or the forward limit position 14 is continued, so the shape of the cavity 3 is “predetermined shape”. Maintaining no change. Therefore, the pressure of the material resin 4 injected and filled in the cavity 3 changes as “the pressure of the material resin sealed in a fixed volume container”. Therefore, for the change in which the pressure of the material resin 4 in the cavity 3 becomes small, the force (sealing force 7 or compression force 11) for sealing the cavity 3 changes (becomes small), so that the material resin 4 itself The contribution of pressure change due to temperature change increases. As a result, even if an operation for reducing the mold clamping force 7 or the compression force 11 is performed during the cooling process, the effect of the operation appearing as a pressure change (decrease) in the material resin 4 filled in the cavity 3 is too great. Don't be.

  The present invention has been made in view of the above problems, and a mechanism in which the operation of the mold clamping mechanism or the compression mechanism in the injection molding method or the injection compression molding method directly affects the pressure change of the material resin filled in the cavity. Injection molding method that realizes obtaining a molded product of good shape quality by giving the mold to be used without complication and appropriately controlling the pressure of the material resin during the whole process of the molding process An object is to provide an injection molding apparatus.

  In order to achieve the above object, according to the first aspect of the present invention, a molten material resin is injected and filled into a cavity of a predetermined shape formed between the fixed mold and the movable mold, and the material resin is injected into the cavity. In the molding method that is cooled and solidified in the mold and taken out of the mold, the mechanism for setting the shape of the cavity is controlled based on the cavity thickness throughout the entire process from the start of the injection filling process to the completion of the cooling process. It is characterized by. Such a configuration makes it possible to control the cavity volume and the pressure of the material resin in the cavity.

  According to the second aspect of the present invention, the molten material resin is injected and filled into a cavity having a predetermined shape formed between the fixed mold and the movable mold, and the material resin is cooled and solidified in the cavity. In a molding method to be taken out of the mold later, after a predetermined amount of molten material resin is injected and filled into the cavity, the cavity forming portion of the movable mold is advanced to a thickness equal to or less than the predetermined molded product thickness, An operation of compressing the material resin is performed. With such a configuration, it is possible to generate a high pressure on the material resin in the cavity to transfer the cavity shape, and to give room for control to reduce the pressure of the material resin in the cavity by the subsequent cavity thickness control operation. It becomes possible.

  According to the invention of claim 3, in the invention of claim 1 or 2, in accordance with the pressure change of the material resin and the progress of cooling during the cooling step after compressing the material resin injected and filled in the cavity. Then, the movable cavity forming portion is retracted to increase the cavity thickness. With such a configuration, the pressure of the material resin in the cavity can be lowered.

  According to the invention according to claim 4, in the invention according to claim 3, the cavity thickness becomes a predetermined molded product thickness at the completion of the cooling step, and the molded product shape after the internal pressure of the material resin in the cavity is taken out is deformed. The retracting operation of the movable cavity forming portion is controlled so as to be lowered to a level not to be performed. With such a configuration, it is possible to obtain a molded product having a good shape quality with a predetermined shape.

  According to the invention according to claim 5, in the invention according to claim 3 or 4, before reaching the temperature at which the material resin loses fluidity, the internal pressure of the material resin is reduced to a predetermined pressure or less. It is characterized by controlling the backward movement of the movable cavity forming portion. With such a configuration, it is possible to obtain a molded product having good shape quality by avoiding deformation of the molded product taken out of the cavity due to internal stress.

  According to the invention according to claim 6, in the invention according to any one of claims 1 to 5, a cavity is formed by combining a fixed mold and a movable mold, and the cavity is maintained by a mold clamping mechanism. It is characterized by. With such a configuration, the invention according to claims 1 to 5 can be realized by injection molding.

  According to the invention according to claim 7, in the invention according to any one of claims 1 to 5, the movable mold includes a surface that becomes a part of the cavity and is movable with respect to the movable mold body. The cavity shape is determined by combining the fixed mold and the movable mold and moving the compression core. With such a configuration, the invention according to claims 1 to 5 can be realized by injection compression molding.

  According to the invention according to claim 8, the mold includes a fixed mold, a movable mold, and a mold clamping mechanism that combines the fixed mold and the movable mold to maintain a cavity formed between the two in a predetermined shape. In the injection molding apparatus for injecting and filling molten material resin into the cavity, and cooling and solidifying the material resin in the cavity and taking it out of the mold, all processes from the start of the injection filling process to the completion of the cooling process And a control mechanism capable of controlling the mold clamping mechanism on the basis of a cavity thickness or a position of a movable platen that fixes the movable mold with respect to the apparatus main body. With such a configuration, it is possible to provide an injection molding apparatus that realizes the inventions according to claims 1 to 5.

  According to the invention of claim 9, a fixed mold, a movable mold, a compression core that is provided on the movable mold, includes a surface that becomes a part of a cavity, and is movable with respect to the movable mold body; A combination of a fixed mold and the movable mold, and a compression mechanism for determining a cavity shape by moving the compression core, injecting and filling a molten material resin into the cavity, and moving the compression core In an injection compression molding apparatus that maintains a predetermined cavity shape and cools and solidifies the resin material in the cavity and then takes it out of the mold, the cavity thickness or through the entire process from the start of the injection filling process to the completion of the cooling process It has a control mechanism which can control the compression mechanism on the basis of the compression rod position. With such a configuration, an injection compression molding apparatus that realizes the invention according to claims 1 to 5 can be provided.

  According to the tenth aspect of the present invention, a fixed mold and a movable mold are used, and a molten material resin is injected and filled into a cavity formed between the fixed mold and the movable mold, and the material resin is injected into the cavity. In a mold for injection molding that is injection-molded by cooling and solidifying inside, in a state where a cavity having a predetermined thickness and shape is formed, the parting surfaces of the fixed mold and the movable mold are not in contact with each other. A predetermined interval is maintained between the two. With such a configuration, it is possible to provide a mold used in an injection molding apparatus that realizes the inventions according to claims 1 to 5.

  According to the invention of claim 11, it comprises a fixed mold, a movable mold, and a compression core that is provided on the movable mold and includes a surface that becomes a part of a cavity and is movable with respect to the movable mold body. The cavity shape is determined by combining the fixed mold and the movable mold, and the compressed core is moved, and the molten material resin is injected and filled into the cavity, and the compressed core is moved to obtain a predetermined cavity shape. The compression core of the movable mold in a state where a cavity having a predetermined thickness and shape is formed in an injection compression molding mold in which injection molding is performed by cooling and solidifying the material resin in the cavity The portion does not reach the forward limit, and a predetermined advanceable width is maintained in the compression core. With such a configuration, it is possible to provide a mold used in an injection compression molding apparatus that realizes the inventions according to claims 1 to 5.

  According to the invention concerning Claim 12, it shape | molded by the shaping | molding method of any one of Claims 1-7, It is characterized by the above-mentioned. With such a configuration, it becomes possible to obtain an optical disc master having a good shape quality, and the characteristics obtained from this good shape quality can be utilized for the production of an optical disc.

  The invention according to claim 13 is characterized in that the optical disc master according to claim 12 is used. With such a configuration, it becomes possible to obtain an optical disk with good shape quality.

  In claim 1, a melted material resin is injected and filled in a cavity of a predetermined shape formed between the fixed mold and the movable mold, and the material resin is cooled and solidified in the cavity and then taken out of the mold. In the molding method, the volume of the cavity is controlled by controlling the mold clamping mechanism or compression mechanism of the molding apparatus based on the cavity thickness throughout the entire process from the start of the injection filling process to the completion of the cooling process. It becomes possible to directly control the pressure of the resin.

  According to a second aspect of the present invention, a melted material resin is injected and filled into a cavity of a predetermined shape formed between the fixed mold and the movable mold, and the material resin is cooled and solidified in the cavity and then taken out of the mold. In the molding method, after a predetermined amount of molten material resin is injected and filled into the cavity, the movable cavity forming member is advanced to a thickness equal to or less than the predetermined molded product thickness to compress the material resin in the cavity. By performing the operation, it is possible to generate a high pressure on the material resin in the cavity to transfer the cavity shape, and to control the pressure of the material resin in the cavity to be reduced by the subsequent cavity thickness control operation. .

  According to claim 3, in the molding method described in claim 1 and claim 2, during the cooling step after compressing the material resin injected and filled in the cavity, the pressure change of the material resin and the progress of cooling are matched. By performing the operation of retracting the movable cavity forming member to increase the cavity thickness by enlarging the cavity thickness, the pressure of the material resin in the cavity can be reduced under optimum conditions.

  According to a fourth aspect of the present invention, in the molding method described in the third aspect, the cavity thickness becomes a predetermined molded product thickness when the cooling process is completed, and the internal pressure of the material resin in the cavity is at a level at which the molded product shape after taking out is not deformed. By controlling the retracting operation of the movable cavity forming member so as to decrease to a low level, it is possible to obtain a molded product having a good shape quality of a predetermined shape.

  According to claim 5, in the molding method described in claim 3 and claim 4, before reaching a temperature at which the material resin loses its fluidity, it is movable so that the internal pressure of the material resin is reduced to a predetermined pressure or less. By controlling the backward movement of the cavity forming member of the mold, it is possible to obtain a molded product having good shape quality by avoiding deformation of the molded product taken out of the cavity due to internal stress.

  In claim 6, the molding method according to claims 1 to 5 is an injection molding method, and in claim 7, the molding method according to claims 1 to 5 is an injection molding compression method.

  According to an eighth aspect of the present invention, there is provided an injection molding apparatus having a control mechanism capable of controlling the mold clamping mechanism based on the cavity thickness or the movable platen position throughout the entire process from the start of the injection filling process to the completion of the cooling process. The apparatus for implement | achieving shaping | molding by the method described in claim | item 1 to 5 is provided.

  According to a ninth aspect of the present invention, there is provided an injection compression molding apparatus having a control mechanism capable of controlling the compression mechanism based on the cavity thickness or the compression rod position throughout the entire process from the start of the injection filling process to the completion of the cooling process. The apparatus for implement | achieving shaping | molding by the method described in claim | item 1 to 5 is provided.

  According to a tenth aspect of the present invention, in a state where the cavity is formed with a predetermined thickness and shape, the fixed part and the movable parting surface are not in contact with each other, and a predetermined interval is maintained between them. An injection mold for realizing molding by the method described in claims 1 to 5 is provided as an injection mold.

  In claim 11, in a state where the cavity is formed with a predetermined thickness and shape, the movable compression core portion does not reach the forward limit, and the predetermined advanceable width is maintained in the compression core. An injection compression molding die for realizing molding by the method described in claims 1 to 5 is provided as a featured injection compression molding die.

  According to the twelfth aspect of the present invention, there is provided an optical disc master molded by the injection molding method or the injection compression molding method described in the first to seventh aspects, and the characteristics obtained from the good shape quality can be utilized for the production of the optical disc.

  According to the thirteenth aspect, an optical disc manufactured using the optical disc master described in the twelfth aspect can obtain an optical disc having a good shape quality due to the characteristics obtained from the good shape quality of the used optical disc master. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a conceptual diagram showing a main part configuration of a molding apparatus and an injection molding (pseudo compression molding) process by the molding apparatus according to the first embodiment of the present invention, and 17 shows a slide cavity wall. The same members as those in the prior art shown in FIGS. 4 to 7 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The molding apparatus in the first embodiment is an apparatus using an injection molding method. In an injection mold in a molding apparatus using an injection molding method, as an important element for forming a mold, the cavity thickness from the mold open state shown in FIG. 1A to the compressed state shown in FIG. A slide cavity wall 17 constituting the cavity 3 corresponding to the change is provided. Specifically, a convex slide cavity wall 17 is formed in the fixed mold 1, and a concave portion in which the slide cavity wall 17 is fitted is formed in the movable mold 2, and the movable mold 2 surrounded by the concave portion. The cavity 3 of the closed space is constituted by the surface of the fixed mold 1 surrounded by the surface of the slide cavity wall 17 and the surface of the slide cavity wall 17.

  First, in the injection molding method, a predetermined cavity thickness 15 or cavity thickness is expanded from the predetermined cavity thickness 15 by a mold opening amount 12 using a mold clamping mechanism (not shown), and the cavity forming portion of the movable mold 2 is stopped in this expanded state. Then, a predetermined amount of material resin 4 is injected and filled (FIG. 1 (a)), and then the cavity forming portion of the movable mold 2 is advanced to a position where the cavity thickness is reduced by an amount 16 defined by a predetermined cavity thickness 15. Then, the material resin 4 injected and filled in the cavity 3 is compressed (FIG. 1B).

  Here, in the usual injection molding method described in the background art section, the mold clamping mechanism is controlled by the mold clamping mechanism after the operation of stopping the cavity 3 of the movable mold 2 at the set position during the injection filling operation. The process is performed based on the magnitude of the “force (clamping force)” to be generated. In the present embodiment, the mold clamping mechanism is controlled based on the thickness of the cavity 3 in all steps. Further, as a method for controlling the mold clamping mechanism based on the cavity thickness, a distance between the fixed mold 1 and the movable mold 2 can be determined by a contact or non-contact position sensor (not shown) provided in the mold. The cavity thickness is obtained by measurement, and the mold clamping mechanism is controlled based on the measured value, or the mold shape, mold closing position, and movable platen (not shown. Plate for fixing the movable mold 2 to the molding apparatus) There is a method for controlling the clamping mechanism based on the correlation between the movable platen position calculated from the positional relationship and the cavity thickness.

  Further, in a mold used in a usual injection molding method, the movable mold 2 and the parting surface 13 of the fixed mold 1 are in contact with each other at a position where the cavity thickness reaches a predetermined thickness 15, and the movable mold 2 is further advanced. That is, it is impossible to make the cavity thickness thinner than the predetermined thickness 15 (FIG. 7A). On the other hand, the mold used in this embodiment is in a state where the cavity 3 is formed with a predetermined thickness and shape, and the parting surfaces of the fixed mold 1 and the movable mold 2 are not in contact with each other, and a predetermined gap is provided between them. Therefore, the material resin 4 injected and filled in the cavity 3 can be compressed until the cavity thickness becomes a predetermined thickness 15 or less.

  A state in which pressure 6 is generated by compressing the material resin 4 in the cavity 3 by advancing the cavity forming portion of the movable mold 2 to a position where the cavity thickness is reduced by an amount 16 defined by a predetermined cavity thickness 15 (FIG. 1). (B)) is held for a time necessary and sufficient to transfer the cavity shape to the molded product, and then the cavity forming portion of the movable mold 2 is moved backward by a mold clamping mechanism (not shown) to increase the cavity thickness (FIG. 3 ( a)). The operation of expanding the cavity thickness is an operation of increasing the cavity capacity occupied by the material resin 4. In other words, from the standpoint of the material resin 4, the volume expands (adiabatic) and the pressure of the material resin 4 decreases. . That is, control is performed to directly reduce the pressure of the material resin 4 by an operation of increasing the cavity thickness of the mold clamping mechanism. Further, in parallel with the pressure drop of the material resin 4 by the above-described mold clamping mechanism control, the temperature of the material resin 4 decreases with time from the initial molten state, and the pressure also decreases. Therefore, while considering the pressure drop due to this temperature drop, the cavity thickness becomes the thickness of the predetermined molded article 8 when the cooling process is completed (FIG. 3B), and at the same time, the internal pressure of the material resin in the cavity 3 is The retraction control of the cavity forming portion of the movable mold 2 is performed by the mold clamping mechanism so that the shape of the molded product after taking out is lowered to a level that does not deform. As a result, the obtained molded product has a good shape quality obtained by accurately transferring a predetermined cavity shape.

  In addition, the pressure drop control of the material resin 4 by increasing the cavity thickness starts from a state in which a predetermined volume of the material resin 4 is compressed to a smaller volume, and the volume is increased until a predetermined molded product thickness, that is, a predetermined volume is reached. To do. During this process, the material resin 4 is always compressed from its normal volume. For this reason, the occurrence of “sinks” that often appear in usual injection molding in the decompression process during the cooling step cannot occur.

  FIG. 2 is a conceptual diagram showing a main part configuration of a molding apparatus and an injection compression molding process by the molding apparatus in the second embodiment of the present invention. The same members as those in the prior art shown in FIGS. 4 to 7 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The molding apparatus in the second embodiment is an apparatus using an injection compression molding method.

  In the molding method according to the second embodiment, first, the material resin 4 is injected and filled in a state in which the compression core 9 is retracted by a predetermined compression margin 10 and the thickness of the cavity 3 is increased (FIG. 2A), and a predetermined amount. The material resin 4 injected and filled into the cavity 3 by advancing the compression core 9 to a position where the cavity thickness is reduced by a compression amount 16 defined by a predetermined cavity thickness 15 at the timing when the material resin 4 is filled in the cavity 3. Is compressed (FIG. 2B). In the usual injection compression molding method, the control of the compression core 9 is performed based on the magnitude of the “force (compression force)” that is generated by the compression mechanism. The compression mechanism is controlled based on the thickness. The method of controlling the compression mechanism based on the cavity thickness is similar to the injection molding method shown in FIG. 1, using a directly measured cavity thickness measurement value, mold geometry and compression rod (not shown, compression). There is a method of using a calculated value obtained from a correlation between positions) in which a force is applied in direct contact with 9 parts of the compression core in part of the mechanism.

  Further, in the mold used in the usual injection compression molding method, the compression core 9 hits the advance limit position 14 at a position where the cavity thickness reaches a predetermined thickness 15, and the compression core 9 is further advanced, in other words, the cavity. It is impossible to make the thickness thinner than the predetermined thickness 15 (FIG. 7B). In contrast, in the mold used in the second embodiment, the cavity 3 is formed with a predetermined thickness and shape, and the compression core 9 and the forward limit position 14 are not in contact with each other, and a predetermined interval is provided therebetween. Therefore, the material resin 4 injected and filled in the cavity 3 can be compressed until the cavity thickness becomes a predetermined thickness 15 or less.

  The operation after the compression of the material resin 4 injected and filled in the cavity 3 until the cavity thickness becomes equal to or less than the predetermined thickness 15 is substantially the same as that of the first embodiment described above. By replacing the “clamping mechanism” in the embodiment with a “compression mechanism” and the “cavity forming portion of the movable mold 2” with a “compression core”, an explanation will be given regarding the injection compression molding method in the second embodiment. Therefore, the occurrence of “sink marks” often appearing in conventional injection compression molding during the decompression process during the cooling process cannot occur.

  By the way, although the molding was actually performed by the method according to the first and second embodiments described above, there were cases in which the shape quality of the obtained molded product did not reach the target quality. When the cause was analyzed, the temperature of the material resin 4 injected and filled in the cavity 3 decreased, and the pressure of the material resin 4 at the time when it reached the temperature at which the fluidity was lost (the material resin used) It was clarified that the obtained molded product is greatly deformed under the above conditions (determined by the type, physical properties and shape of the molded product). In other words, in the pressure drop process while the material resin 4 maintains fluidity, the molecular chain of the material resin 4 can move relatively freely to relieve the internal pressure. On the other hand, after the fluidity is lost, the movement of the molecular chain inside the material resin 4 is limited and pressure relaxation does not proceed, and it remains as an internal stress, and this internal stress is taken out of the cavity. Cause deformation.

  Therefore, before the temperature of the material resin 4 drops to a temperature at which the fluidity is lost, an operation of retracting the cavity forming portion of the movable mold 2 at a relatively high speed is performed to reduce the pressure of the material resin 4 below a certain level. Decrease rapidly until Subsequently, the cavity forming portion of the movable mold 2 is controlled to retract at a relatively slow speed while being combined with the temperature drop of the material resin 4 and the pressure drop caused by the temperature drop.

  Then, the mold clamping mechanism is controlled based on the cavity thickness as described above, and the cavity shape is precisely transferred by directly and optimally controlling the pressure of the material resin 4 injected and filled in the cavity 3. Molded products with good shape quality can be obtained without molding defects such as “sink marks”. In addition, the molded product obtained by this molding method has very excellent characteristics even when used as a molded product that requires precise shape accuracy such as optical parts and elements. Products that use products also have excellent quality.

  Next, a specific example in the case of producing an optical disk substrate using the molding apparatus and molding method according to the first embodiment of the present invention will be described.

A high density optical disk substrate having a thickness of 0.60 mm is injection molded (pseudo compression molding) at a mold temperature of 123 ° C. The mold clamping mechanism is operated and the cavity thickness is expanded to 0.62 mm. A predetermined volume of polycarbonate material is injected and filled (maximum cylinder setting temperature: 380 ° C.), and the cavity thickness is advanced to 0.57 mm. Compress the resin. After maintaining this state for 0.15 sec, the cavity thickness is rapidly expanded by controlling the mold clamping mechanism so that the resin pressure decreases to 70 kg / cm ² or less before the material resin temperature decreases to approximately 160 ° C. Further, the cavity thickness is increased at a relatively slow speed while being combined with the temperature drop of the material resin and the pressure drop due to the temperature drop. When the cooling process is completed (cooling time 10 seconds), the cavity thickness is 0.60 mm and the resin pressure is The mold clamping mechanism was controlled so as to be 5 kg / cm ² or less, and a high-density optical disk substrate was molded. The cavity thickness was controlled based on the movable platen position calculated from the correlation between the mold shape and the movable platen position. The obtained high-density optical disk substrate accurately transferred the required fine shape such as guide grooves, and at the same time, became an optical disk substrate having excellent flatness with little warpage and undulation.

  The present invention relates to a molding method, a molding apparatus, and a molded product of a molded product that requires high shape accuracy and precise transfer of a fine pattern, such as an optical element such as an optical disk and an optical lens.

FIG. 1 is a conceptual diagram showing a main configuration of a molding apparatus according to a first embodiment of the present invention and an injection molding (pseudo compression molding) process by the molding apparatus. The key map showing the principal part composition of the molding device in a 2nd embodiment of the present invention, and the injection compression molding process by this molding device. Conceptual diagram showing the process after molding Process chart showing injection molding process Process diagram showing the main steps of the injection compression molding process Process diagram showing the main steps of the pseudo compression molding process Conceptual diagram showing the state of the cavity during the cooling process

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixed type | mold 2 Movable type | mold 3 Cavity 4 Material resin 5 Injection pressure 6 Pressure 7 Clamping force 8 Molded product 9 Compression core 10 Compression margin 11 Compression force 12 Parting surface 14 Advance limit position 15 Cavity thickness 16 Specified compression Quantity 17 Slide cavity wall

Claims (13)

  In a molding method in which a melted material resin is injected and filled into a cavity of a predetermined shape formed between a fixed mold and a movable mold, and the material resin is cooled and solidified in the cavity and then taken out of the mold. A molding method characterized in that the mechanism for setting the shape of the cavity is controlled based on the cavity thickness throughout the entire process from the start of the injection filling process to the completion of the cooling process.   In a molding method in which a melted material resin is injected and filled into a cavity of a predetermined shape formed between a fixed mold and a movable mold, and the material resin is cooled and solidified in the cavity and then taken out of the mold. After a predetermined amount of injected material resin is injected and filled into the cavity, the movable cavity forming portion is advanced to a thickness where the cavity thickness is equal to or less than the predetermined molded product thickness, and the operation of compressing the material resin in the cavity is performed. A characteristic molding method.   During the cooling process after compressing the material resin injected and filled in the cavity, the movable cavity forming part is retracted to expand the cavity thickness according to the pressure change of the material resin and the progress of cooling. The molding method according to claim 1, wherein the molding method is characterized.   When the cooling process is completed, the movable cavity forming part moves backward so that the cavity thickness reaches the predetermined molded product thickness and the internal pressure of the resin material in the cavity drops to a level at which the molded product shape does not deform after removal. The molding method according to claim 3, wherein control is performed.   4. The retracting operation of the movable cavity forming portion is controlled so that the internal pressure of the material resin drops to a predetermined pressure or less before reaching the temperature at which the material resin loses fluidity. Or the shaping | molding method of 4.   The molding method according to claim 1, wherein a cavity is formed by combining a fixed mold and a movable mold, and the cavity is maintained by a mold clamping mechanism.   The movable mold includes a compression core that includes a surface that becomes a part of the cavity and is movable with respect to the movable mold body. The cavity shape is determined by combining the fixed mold and the movable mold and moving the compression core. The molding method according to claim 1, wherein: A fixed mold, a movable mold, and a mold clamping mechanism for maintaining a cavity formed between the fixed mold and the movable mold in a predetermined shape, and injecting a molten material resin into the cavity In an injection molding device that fills and cools and solidifies the material resin in the cavity and then takes it out of the mold,
A control mechanism capable of controlling the mold clamping mechanism based on the cavity thickness or the position of the movable platen that fixes the movable mold to the apparatus body throughout the entire process from the start of the injection filling process to the completion of the cooling process. An injection molding apparatus comprising: A fixed mold, a movable mold, a compression core that is provided in the movable mold, includes a surface that becomes a part of a cavity and is movable with respect to the movable mold body, and the fixed mold and the movable mold are combined. A compression mechanism for determining a cavity shape by moving the compression core, injecting and filling a melted material resin into the cavity, moving the compression core to maintain a predetermined cavity shape, and the material In the injection compression molding device that takes out the resin after cooling and solidifying the resin in the cavity,
An injection compression molding apparatus comprising a control mechanism capable of controlling the compression mechanism based on a cavity thickness or a compression rod position throughout the entire process from the start of an injection filling process to the completion of a cooling process. It consists of a fixed mold and a movable mold. Injection is performed by injecting and filling molten material resin into a cavity formed between the fixed mold and the movable mold, and cooling and solidifying the material resin in the cavity. In the mold for injection molding,
A molding die characterized in that in a state where a cavity having a predetermined thickness and shape is formed, the parting surfaces of the fixed mold and the movable mold do not contact each other, and a predetermined interval is maintained between them. . A fixed mold, a movable mold, and a compression core that is provided on the movable mold and includes a surface that is a part of a cavity and is movable with respect to the movable mold body. In combination, the cavity shape is determined by moving the compression core, the molten material resin is injected and filled into the cavity, the compression core is moved to maintain the predetermined cavity shape, and the material resin is moved into the cavity. In the mold for injection compression molding that is injection-molded by cooling and solidifying with
In a state in which a cavity having a predetermined thickness and shape is formed, the movable compression core portion does not reach the advance limit, and a predetermined advanceable width is maintained in the compression core. Mold for molding.   An optical disc master formed by the molding method according to claim 1.   An optical disc comprising the optical disc master according to claim 12.

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