JPH05237894A - Method and apparatus for molding substrate for data recording medium - Google Patents

Abstract

PURPOSE:To produce a substrate for a data recording medium not generating the transfer shift of a small signal mark or the like, reduced in double refraction, generating no warp or undulation and excellent in optical characteristics in low cost by injection compression molding. CONSTITUTION:In a method for molding a substrate for a data recording medium by providing the mold cavity constituted by a mold member consisting of a fixed mold 18 and a movable mold 17 both of which are opposed to each other to a toggle type injection molding machine equipped with a toggle mechanism extending a toggle link 3 to obtain mold clamping force by the tensile strength of tie bars 5a, 5b and injecting a molten thermoplastic resin material in the mold cavity to perform compression molding, the molten resin is injected in the mold cavity to fill the mold cavity under initial set pressure. Thereafter, the molten resin in the mold cavity is subjected to stepwise compression control on the basis of a compression program profile set in a multistage fashion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method and apparatus for an information recording medium substrate such as an optical disk or a magnetic disk, which is made of a thermoplastic resin such as a polycarbonate resin, and is particularly excellent in optical characteristics. The present invention relates to a method for forming a substrate for an information recording medium and an apparatus therefor.

[0002]

2. Description of the Related Art Many inventions have been proposed and have been disclosed as to the prior art relating to the injection molding method of a substrate for information recording medium and its molding apparatus. Among them, a toggle type injection molding machine is used to inject and fill molten resin into the mold cavity, and the mold clamping force is adjusted according to the resin filling pressure to open and close the mold mating surface, and the mold cavity volume is adjusted. A method for molding a substrate for an information recording medium having good optical characteristics by a so-called injection compression molding method in which the value is variable has been proposed (for example, Japanese Laid-Open Patent Publication No. 63-135211, Japanese Utility Model Publication No. 2-61).
632 and the like). In the injection compression molding of the information recording medium substrate by the above-mentioned toggle type injection molding machine, the movable platen or fixed platen of the injection molding machine is divided as a means for controlling the opening and closing of the mold matching surface,
A hydraulic cylinder, an electric screw jack, or the like is added to the divided surface, and the stroke is made variable to control the opening / closing of the die matching surface. As another conventional example, there is also a method of controlling the hydraulic pressure of a hydraulic cylinder for opening and closing a toggle link to open the mold. Here, an example of a conventional toggle type injection molding apparatus will be given and specifically described with reference to FIGS. 5 and 6. 5 shows the configuration of the mold clamping force mold thickness adjustment control system of the mold clamping mechanism of the toggle type injection molding apparatus, and FIG. 6 is a view as seen from the arrow B of FIG. In the figure, if the toggle link 3 is still extended, the mold matching surface for compression molding cannot be opened and closed. Therefore, a hydraulic cylinder is unavoidably provided on the movable platen 13, and the compression ram 14 is moved forward or backward by this hydraulic pressure. In addition, a compressive force is applied to or reduced from the molten resin injected and filled in the mold cavity. The configuration of the retightening mechanism that also functions as the mold thickness adjustment mechanism in the toggle-type injection molding machine has its own characteristics depending on the molding machine manufacturer, but the purpose is to optimize it according to the thickness of the mold used. It is a mechanism for obtaining a strong mold clamping force. In the toggle type injection molding machine shown in FIG. 5, the means for obtaining the mold clamping force is performed by horizontally moving the tail stock 2 on the slide rails 11a to 11b via the guides 12a to 12b. That is, the signal for obtaining the target mold thickness and mold clamping force is given by the additional tightening amount and mold closing position setting device 21.
To drive the induction motor 8. The driving force of the induction motor 8 rotates the pinion gear 9, and the pinion gear 9 meshes with a main gear 10 having a gear on its outer peripheral surface. The main gear 10 is further screwed into four tie bars 5a to 5d. It also meshes with gears provided on the outer peripheral surfaces of the toggle nuts 6a to 6d. Therefore, when the induction motor 8 is rotated, the toggle nuts 6a to 6d move to the tie bars 5a to 5d.
The tailstock 2 is moved horizontally by rotating about 5d as an axis. The forward and backward directions are determined by the rotation direction of the induction motor 8.

[0003]

In the above-mentioned prior art, the purpose of opening and closing the die mating surface can be achieved.
There is a problem that the structure becomes complicated due to the addition of a hydraulic mechanism etc. to the movable platen, and as a result the shape and size increase, and in addition, since many component parts are used, the rigidity and strength of the entire platen decrease. There was a drawback that
In addition, regarding the method of controlling the hydraulic pressure of the hydraulic cylinder for opening and closing the toggle link, there is a problem that the motion for controlling the mold clamping force by opening and closing the toggle link is large and the operation is rough and precise control cannot be performed. It was Generally, the following two methods can be considered as means for injection compression. (1) It is a method of expanding the mold cavity volume in advance before entering the injection step, injecting and filling the molten resin into the mold cavity volume, and then reducing the mold cavity volume by a compression force. Using a die having a cavity core that slides inside, a hydraulic mechanism in which the cavity core in the die is provided in the die while the die mating surface is closed.
Alternatively, the compression force is applied outside the mold, that is, by a hydraulic mechanism provided on the movable platen of the molding machine or a screw jack. (2) A mold that does not have a cavity core that slides in the mold is used. Before the injection process, the mold is clamped at a low pressure, then resin is injected and filled, and the mold mating surface is formed by the resin pressure. Open and keep the mold clamping force as it is after completion of injection filling, or increase it to close the mold mating surface and apply compressive force to the molten resin. The method of (1) above is a technique that can be implemented by a direct pressure type injection molding machine or a toggle type injection molding machine.
This method is a technique that is difficult to implement with a toggle type injection molding machine. That is, in the toggle type mold clamping mechanism, the toggle link is extended and the mold clamping force is obtained by the tensile strength of the tie bar, so that the mold mating surface is formed by the resin pressure injected and filled in the initial low pressure mold clamping state. In order to open it, it is necessary to extend the tie bar, and if the tie bar extends, the mold clamping force inevitably increases, the mold mating surface cannot be opened, and there is a problem that the control thereafter cannot be performed.

An object of the present invention is to solve the problems in the conventional toggle type injection molding machine, in which the original rigidity and strength are maintained without any processing on the movable platen. In addition, it is configured to freely control the opening and closing of the mating surface of the mold without providing a cavity core that slides in the mold, and injection filling into the mold cavity based on the compression program profile set in multiple stages. Another object of the present invention is to provide a new injection molding method that enables molding of a substrate for an information recording medium having excellent optical characteristics by controlling compression of the molten resin in stages and an apparatus for carrying out the method.

[0005]

The object of the present invention is to improve the precision of the mold clamping force re-tightening mechanism used in the conventional toggle type injection molding machine and to drive the mold clamping force re-tightening mechanism. This is achieved by adaptive control in the control software aspect. In other words, the movement accuracy of the forward and backward movements of the tailstock, which is a component of the mold clamping mechanism, is improved, and the response speed required for the movement is increased, and the drive control of the mold clamping force increasing clamping mechanism is performed in the mold cavity. It is realized by detecting the pressure of the resin injected into the cylinder, the opening of the mold mating surface, the amount of tie bar expansion, etc., and comparing and controlling the electric signal based on it and the programmed external electric signal. Is.

The present invention is a toggle type injection molding machine equipped with a toggle mechanism that extends a toggle link and obtains a mold clamping force by the tensile strength of a tie bar, and is composed of a mold member having a fixed side and a movable side facing each other. In a method of forming a mold cavity, injecting and filling a molten resin made of a thermoplastic resin material into the mold cavity, and performing compression molding to mold a substrate for an information recording medium, melting in the mold cavity After injecting the resin and filling it to the initial set pressure, based on the compression program profile set in multiple stages,
It is a method of molding a substrate for an information recording medium, which includes at least a step of stepwise controlling compression of a molten resin in a mold cavity. In the method for molding a substrate for an information recording medium of the present invention, the initial mold clamping force is set to almost zero, and the mold cavity is injected and filled with molten resin, and then the mold clamping force is increased in 4 to 10 steps or A method of controlling compression based on a decreasing compression program profile is preferred. As described above, when the compression molding is performed in multiple stages, the transfer deviation (multiple transfer) of minute signal marks and the like is eliminated, the birefringence is small, and the substrate is not warped or wavy, and the optical characteristics are excellent. A highly accurate and high-quality information recording medium substrate can be obtained.

Further, according to the present invention, a toggle is provided with a toggle mechanism for extending a toggle link of a die cavity composed of a die member having a fixed side and a movable side facing each other to obtain a die clamping force by a tensile strength of a tie bar. In a toggle-type injection molding apparatus that is mounted on a type injection molding machine, injection-fills a molten resin made of a thermoplastic resin material into the mold cavity, and performs compression molding to mold a substrate for an information recording medium, With the toggle link of the mold clamping toggle mechanism of the toggle type injection molding device extended, means for moving the movable platen having the movable mold member attached thereto forward or backward is provided to change the volume of the mold cavity. And a control device for controlling the information recording medium. Then, in the apparatus for molding a substrate for an information recording medium of the present invention,
Means for advancing or retracting the movable platen equipped with the movable mold member is, for example, rotationally controlling the tie bar nut for positioning the tail stock of the mold clamping toggle mechanism, and the tail stock main body of the toggle type injection molding machine. The structure is such that it moves forward or backward on the base. Also, the movement control of the above tailstock is
For example, at least one signal selected from an internal pressure signal of the mold cavity, an opening amount signal of the mold mating surface, a tie bar extension amount signal, etc. is a drive source of the tail stock moving mechanism that controls the mold clamping force. The configuration is such that the movement amount of the movable platen is continuously controlled by inputting it to the servo motor.

[0008]

The principle of generation of the mold clamping force in the toggle type injection molding apparatus of the present invention is as described above, in which the movable side mold member is pressed against the fixed side mold member, and the toggle link is further extended to form the fixed platen. A mold clamping force is generated by stretching the tie bar connecting the tail stocks by a desired length. Therefore, the position of the tailstock is clamped while the toggle link is stretched and changed to the mold opening direction regardless of whether the molding is continuing or the molding is stopped, and the operation of this tailstock is injected into the mold cavity. By synchronously controlling the injection filling operation based on the electric signal based on the pressure of the filled resin, the opening amount of the mold mating surface, the extension amount of the tie bar, or an external electric signal that is arbitrarily set, It is possible to realize a method of molding a substrate for an information recording medium in which compression control is performed in multiple stages, eliminate transfer deviation (multiple transfer) of minute signal marks, reduce birefringence, and prevent warpage and waviness of the substrate.
It is possible to obtain a high-quality and high-quality information recording medium substrate having excellent optical characteristics, and to achieve the object of the present invention.

[0009]

Embodiments of the present invention will be described below in more detail with reference to the drawings. <Embodiment 1> FIG. 1 shows an example of the structure of a tailstock moving mechanism that constitutes a mold clamping mechanism of an injection molding apparatus of the present invention, and a control system thereof, which is during injection filling of molten resin or immediately after injection filling. In addition, the tail stock 2 is moved forward or backward, and a compression force is applied to the molten resin filled in the mold cavity while the toggle link 3 is stretched.
Alternatively, the tailstock 2 is characterized by being added with a control system which can be operated more accurately and at a higher speed than in the conventional injection molding apparatus. Next, an example of a mechanism that changes the opening amount of the mold matching surface while the toggle link 3 is stretched, which is the mold clamping force variable mechanism of the present invention, will be described with reference to FIG.
In the figure, the tail stock 2 connected to the movable platen 13 and the toggle link 3 is attached to the upper part of the tail stock 2 on the slide rails 11a to 11b provided on the molding machine base 1. A servomotor 25 is installed as a drive source for moving the vehicle forward or backward in a horizontal direction, and a pinion gear 9 is fitted on the servomotor shaft. The pinion gear 9 meshes with a main gear 10 having a gear on the outer peripheral surface thereof, and the main gear 10 is a gear formed on the outer peripheral surfaces of toggle nuts 6a to 6d screwed into four tie bars 5a to 5d. Since they also mesh with each other, when the servo motor 25 is rotated, the toggle nuts 6a to 6d are moved to the tie bars 5a to 5d.
To rotate the tailstock 2 in the horizontal direction. The forward and backward directions are the servo motor 2
It is determined by the rotation direction of 5. The reason for using the servo motor 25 as the drive source is that the response speed is fast and the repeatability is excellent, but other motors can be used as long as the same performance can be exhibited. It doesn't matter. Also, the pinion gear 9 and the main gear 1
0, the number of gear teeth of the toggle nuts 6a to 6d is preferably as large as possible, and the pitch of the toggle nuts 6a to 6d and the tie bar screw with which the toggle nuts 6a to 6d are fitted is preferably as small as possible.
Should be able to move forward or backward at a speed of 20 mm / sec or more. Of course, it goes without saying that if the speed is further increased, the range of molding conditions will increase accordingly. Further, in order to suppress the loss time of the forward / reverse switching time as small as possible, the main gear 10 is preferably of a backlash-preventing type, and a timing belt or the like is most suitable for preventing backlash. On the other hand, as a control system of the tail stock moving mechanism which is a variable mechanism of the above-mentioned mold matching surface opening amount, a strain gauge 22 for measuring the amount of extension of the tie bar is attached to the tie bars 5a to 5d.
The strain gauge 22 may be a displacement type or a contact type displacement gauge, and any type may be used as long as it has an accuracy capable of measuring a change amount of 1/1000 mm or less. Further, it is most preferable to attach one sensor to each tie bar, but it is also possible to attach it to one of the four tie bars that is representative. Although the mounting position is the end portion on the fixed platen side in this embodiment, it is not specified as long as it can accurately measure the elongation amount. The output from the strain gauge (or displacement gauge) 22 is input to the input / output comparison setting device (compression profile setting device) 29 as a tie bar extension amount signal 28. A displacement meter 23 capable of measuring the amount of opening of the mold matching surfaces of the fixed mold member 18 and the movable mold member 17 is attached to the mold. The displacement gauge 23 may be of any type as long as its accuracy is guaranteed whether it is a contact type or a non-contact type. The measurement accuracy is preferably 1/1000 mm or less. The output from the displacement meter 23 is input to the input / output comparison / setting device 29 as the opening amount signal 26 of the mold matching surface. Further, a pressure sensor 24 for measuring the resin pressure on the cavity surface is attached to the mold. The output from the pressure sensor 24 is input to the input / output comparison setter 29 as a cavity pressure signal 27. The input / output comparison / setting device 29 uses the above-mentioned three types of input signals 2
6, 27, 28, or any one of the signal level values is compared with a preset drive start level value of the servo motor 25, and when the level value of the input signal reaches the set value. Drive the servo motor 23,
This is a control device for programming and executing the course of the amount of opening of the mold matching surface thereafter. The servo motor control input / output converter 30 receives the servo motor 2 according to the setting output signal of the mold matching surface opening amount programmed by the input / output comparison setting device 29.
5 is a controller having a function of controlling 5. On the other hand, the tightening amount and the signal from the mold closing position setting device 21 are input to the servo motor control input / output converter 30 to increase the tightening amount and the mold tightening amount during setup, which is the original function of the toggle type molding machine. Position setting can be performed.

<Embodiment 2> Next, a representative embodiment of molding a substrate for an information recording medium using the injection compression molding apparatus of the present invention shown in Embodiment 1 will be described. The process of molding the substrate by injection compression molding is: mold closing → injection filling →
The process proceeds in the order of gate seal (gate cut) → compression → mold opening. When the molding machine is started up, first, the mold tightening completion position is set by the additional tightening amount and the mold closing position setting device 21. In this case, since the injection compression molding is performed, the toggle link 3 is extended, and the fixed mold member 1 is stretched with the link stretched.
8 and the movable mold member 17 in close contact with each other, and the tie bar 5 at that time
The elongation amounts of a to 5b are set to be zero. That is, it is set so that the mold mating surface can be easily opened by the filling pressure of the molten resin filled in the mold cavity by injection filling. In other words, the mold clamping force is set to zero. The conventional toggle-type injection molding machine could not make such setting due to its structure. In this example,
Although the mold clamping force is set to zero, if the mold matching surface can be opened within the range where the compression allowance can be secured by the injection filling condition, there is no problem even if the initial mold clamping force is generated accordingly. With respect to the input / output comparison setting device 29, the opening amount signal 26 of the mold matching surface, the cavity internal pressure signal 27,
Of the control items of the tie bar extension amount signal 28, which signal is used for control is selected, and the compression control profile is set. Next, how many millimeters or several microns the mold matching surface is opened at the time of injection filling, or how many k
Input whether or not to set to g / cm ² , and program to complete injection filling when the actual value reaches this set value. Next, the injection and filling process is started to inject and fill the mold cavity with the molten resin. When the injection filling is regulated by the opening amount of the mold matching surface, the mold filling surface is opened by the resin pressure in the cavity, and an injection filling completion signal is output when the opening amount of the mold matching surface is reached. When the injection filling is defined by the cavity internal pressure value, the injection filling completion signal is output when the cavity internal pressure reaches the initially set value. Then, the next gate sealing (gate cutting) step is started.
Next, in the compression process, when the method of controlling the opening amount of the mold matching surface is used, the displacement meter during the compression molding is based on the compression profile programmed in the input / output comparison setting device 29 in advance. A signal is output to the servo motor control input / output converter 30 so as to adjust to the program compression profile while being compared with the opening amount of the mold matching surface by the mold opening surface signal 26 output from 23. Upon receiving this signal, the servo motor control input / output converter 30 outputs a motor drive signal to the servo motor 25,
The servo motor 25 rotates only the required amount by the signal. This rotational force is generated by the pinion gear 9, the main gear 10,
It is transmitted to the toggle nuts 6a to 6d to advance the tail stock 2, the movable platen 13, and the movable mold member 17,
The filling resin in the cavity formed by the movable mold member 17 and the fixed mold member 18 is compressed. FIG. 3 shows an example of each sensor output profile in the injection filling and compression steps of the control method of the opening amount of the mold matching surface. As shown in the figure, after the injection filling of the molten resin is completed, the opening amount of the mold matching surface is set to the peak value, and the mold clamping is performed in eight steps to perform compression molding. As described above, when the compression molding is performed in multiple stages, the transfer deviation (multiple transfer) of minute signal marks and the like is eliminated, the birefringence is small, and the substrate is not warped or wavy, and the optical characteristics are excellent. A highly accurate and high-quality information recording medium substrate can be obtained. Next, a method of controlling the compression control by the programmed internal pressure of the mold cavity will be described. In this case, based on the compression profile programmed in the input / output comparison setting device 29 in advance, while comparing with the cavity internal pressure by the cavity internal pressure signal 27 output from the pressure sensor 24 which detects the internal pressure of the mold cavity during the compression molding process. , And outputs a signal to the servo motor control input / output converter 30 so as to adjust the programmed compression profile. The operation sequence of each control mechanism thereafter is the same as the above-described control method of the opening amount of the mold matching surface. FIG. 4 shows an example of each sensor output profile in the injection filling and compression steps when controlled by the internal pressure of the mold cavity. As a result, a high-precision, high-quality information recording medium substrate excellent in optical characteristics was obtained, as in the case where the opening amount of the mold matching surface was controlled.

[0011]

According to the method for molding a substrate for an information recording medium of the present invention, the substrate can be molded by arbitrarily adjusting the opening amount of the mating surfaces during the injection compression molding of the molten resin in multiple stages. Therefore, transfer deviation (multiple transfer) of minute signal marks etc. is eliminated, birefringence is small, substrate warpage, waviness, etc. do not occur and optical characteristics are excellent and highly accurate,
A high quality information recording medium substrate can be obtained. Further, according to the toggle-type injection molding apparatus of the present invention, it is possible to move the molten resin filled in the mold while the toggle link of the mold clamping toggle mechanism is stretched without adopting a mechanism for compressing the molten resin in the mold. Since the movable platen provided with the mold member on the side is moved forward and backward to increase or decrease the mold clamping force to make the volume of the mold cavity variable, a conventional hydraulic mechanism or screw jack mechanism is used. It becomes unnecessary to provide a high-precision and high-quality information recording medium substrate with an inexpensive injection compression molding machine without increasing the shape and size while maintaining the conventional die strength and rigidity.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a mold clamping mechanism unit and a mold matching surface opening amount variable control system of a toggle type injection molding machine having a tailstock moving mechanism illustrated in a first embodiment of the present invention.

FIG. 2 is a view on arrow A in FIG.

FIG. 3 is a graph showing an example of each sensor output profile in the injection filling and compression processes when the control method of the opening amount of the mold matching surface illustrated in the second embodiment of the present invention is used.

FIG. 4 is a graph showing an example of each sensor output profile in the injection filling and compression steps when controlling with the mold cavity internal pressure exemplified in the second embodiment of the present invention.

FIG. 5 is a schematic diagram showing a configuration of a mold clamping mechanism section, a retightening amount, and a mold clamping position control system of a conventional toggle type injection molding machine.

FIG. 6 is a view on arrow B of FIG.

[Explanation of symbols]

 1 ... Molding machine base 2 ... Tail stock 3 ... Toggle link 4 ... Link opening / closing hydraulic cylinder 5a, 5b, 5c, 5d ... Tie bar 6a, 6b, 6c, 6d ... Toggle nut 7 ... Bearing 8 ... Induction motor 9 ... Pinion gear 10 ... main gears 11a, 11b ... slide rails 12a, 12b ... guide 13 ... movable platen 14 ... compression ram 15 ... forward hydraulic chamber 16 ... reverse hydraulic chamber 17 ... movable mold member 18 ... fixed mold member 19 ... fixed platen 20a , 20b, 20c, 20d ... Nut 21 ... Re-tightening amount, mold closing position setting device 22 ... Strain gauge (or displacement gauge) 23 ... Displacement gauge 24 ... Pressure sensor 25 ... Servo motor 26 ... Opening amount signal 27 of mold matching surface … Cavity pressure signal 28… Tie bar extension signal 29… Input / output comparison setting device (compression profile setting device) 30… Ser Motor control output transducer

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area // B29L 17:00 4F

Claims (5)

[Claims] 1. A toggle type injection molding machine equipped with a toggle mechanism for extending a toggle link to obtain a mold clamping force by a tensile strength of a tie bar, and a mold composed of a mold member having a fixed side and a movable side facing each other. In a method of forming a cavity, injecting and filling a molten resin made of a thermoplastic resin material into the mold cavity, and performing compression molding to mold a substrate for an information recording medium, the molten resin is filled in the mold cavity. A substrate for an information recording medium, which includes at least a step of stepwise controlling compression of the molten resin in the mold cavity based on a compression program profile set in multiple stages after injection and filling at an initial set pressure. Molding method. 2. A compression method according to claim 1, wherein an initial set mold clamping force is set to substantially zero, and a mold cavity is injected and filled with molten resin, and then the mold clamping force is increased or decreased in 4 to 10 steps. A method for molding a substrate for an information recording medium, characterized in that compression control is performed based on a program profile. 3. A toggle-type injection molding equipped with a toggle mechanism for extending a toggle link to obtain a mold clamping force by a tensile strength of a tie bar in a mold cavity composed of a fixed side and a movable side that face each other. A toggle type injection molding apparatus which is mounted on a machine and injection-fills a molten resin made of a thermoplastic resin material into the mold cavity to perform compression molding to mold a substrate for an information recording medium. Control for varying the volume of the mold cavity by providing a means for advancing or retracting the movable platen having the movable mold member attached thereto while the toggle link of the mold clamping toggle mechanism of the injection molding device is extended An apparatus for forming a substrate for an information recording medium, comprising at least means. 4. A means for advancing or retracting a movable platen having a movable mold member attached thereto, according to claim 3, wherein a tie bar nut for positioning a tail stock of a mold clamping toggle mechanism is rotationally controlled. An apparatus for molding a substrate for an information recording medium, characterized in that the main body is structured to move forward or backward on a base of a toggle type injection molding machine. 5. The tail stock moving mechanism for controlling the moving amount of the movable platen according to claim 4, among the resin pressure signal in the mold cavity, the opening amount signal of the mold mating surface signal and the tie bar extension amount signal. At least one signal selected from the above is input to a servo motor that is the drive source of the tailstock moving mechanism that controls the movement amount of the movable platen, and the movement amount of the movable platen is continuously controlled. And a device for forming a substrate for an information recording medium.