JPH11262938A - Injection molding method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend a forming cycle as a result of that a mold is resonated even at the time of cooling when molding is performed while the mold is resonated to prevent the gradual cooling of a resin. SOLUTION: In an apparatus performing injection molding while a mold 1 (2, 3) is wholly or partially resonated by ultrasonic vibration, an ultrasonic vibrator 8 converting the high frequency power from an ultrasonic oscillator 10 to vibration and the vibration direction converter 7 connecting the ultrasonic vibrator 8 and the mold 1 are provided. By controlling the high frequency power of the ultrasonic oscillator 10, the amplitude of resonance is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an injection molding method and an injection molding method. More specifically, the present invention relates to an injection molding method and apparatus useful for molding optical information recording products such as magneto-optical disks and digital video disks.

[0002]

2. Description of the Related Art In injection molding of a thermoplastic resin, high cycle and high precision have been promoted, and development of a molding technique which can cope with the demand has been desired. In particular, in recording media such as magneto-optical discs and digital video discs, the recording surface has been made to have narrow lands / groups or short pits in order to increase the recording density. However, problems such as a decrease in transferability (transfer unevenness), optical distortion, and warpage due to residual stress have occurred.

[0003]

In order to prevent such a problem from occurring, the applicant of the present invention disclosed in Japanese Patent Publication No. 6-6309 and Japanese Patent Application Laid-Open No. 9-99458 by ultrasonic vibration during injection molding. A method of forming a mold while resonating the mold has been proposed. These molding methods apply ultrasonic vibration of a constant amplitude and frequency at the time of injection to resonate the mold, and can be said to be an excellent technique in that the flowability of the resin at the time of injection is improved.

On the other hand, in injection molding, it is preferable to resonate the mold at the time of injection from the viewpoint of improving the fluidity of the resin. And may result in a longer molding cycle. In the injection molding method proposed in Japanese Patent Publication No. 6-6309 and Japanese Patent Application Laid-Open No. 9-99458, the treatment of the resonance of the mold due to the ultrasonic vibration during the cooling of the resin is not mentioned.

The present invention has been made in view of the above circumstances, and controls the resonance condition of a mold during injection molding, that is, the magnitude and / or frequency of resonance to change the resonance condition of the mold. It is an object of the present invention to provide a method and apparatus for performing injection molding while performing injection molding.

[0006]

Means for Solving the Problems In order to achieve the above object, the inventors of the present invention have conducted intensive studies, and as a result, the resonance condition (amplitude and / or frequency) of a mold during one cycle of injection molding has been changed. The inventors have found that high-quality products can be molded in a short cycle by applying vibrations to desired places and timings in accordance with the progress of the injection molding cycle, and completed the present invention.

That is, the injection molding method of the present invention is a method of performing injection molding while resonating the whole or a part of a mold by ultrasonic vibration, wherein the injection molding is performed while changing the resonance condition of the mold. There is. Specifically, the amplitude or frequency of the resonance or the amplitude and frequency of the resonance,
There is a method in which molding is performed while changing continuously or stepwise. As a result, molding is performed at a predetermined time on a predetermined portion of the mold at a predetermined time while giving a vibration having an arbitrary vibration and / or frequency, and a product without transfer unevenness is formed in a short molding cycle.

In the above-described injection molding method, it is preferable that the amplitude of the resonance is maximized when the resin is injected into the mold, and is minimized when the resin is cooled, and the frequency of the resonance is adjusted when the resin is injected into the mold. It is preferable to make the maximum and the minimum when cooling the resin. By doing so, the resin is smoothly supplied to the cavity, and the resin in the cavity is cooled quickly.

Further, the injection molding apparatus of the present invention is an apparatus for performing injection molding while resonating the whole or a part of a mold by ultrasonic vibration, wherein the ultrasonic vibration for converting high frequency power from an ultrasonic oscillator into vibration. And a vibration direction converter that couples the ultrasonic vibrator and the die, and controls the high frequency power of the ultrasonic oscillator to change the amplitude of the resonance.

Further, the injection molding apparatus of the present invention is an apparatus for performing injection molding while resonating the whole or a part of a mold by ultrasonic vibration, wherein the fundamental frequency for converting high frequency power from an ultrasonic oscillator into vibration is provided. It has a plurality of different ultrasonic transducers, and a vibration direction converter that couples the plurality of ultrasonic transducers and the mold, and selectively supplies high-frequency power to the ultrasonic transducers from the ultrasonic oscillator. The configuration is such that the frequency of the resonance is changed by giving.

According to the injection molding apparatus having such a configuration, the whole or a part of the mold can be resonated at an arbitrary amplitude or frequency, and the injection molding method can be realized with a simple apparatus.

It is also possible to selectively apply high-frequency power from an ultrasonic transmitter to a plurality of ultrasonic transducers having different fundamental frequencies and to control the output of the high-frequency power. . By doing so, the resonance frequency and amplitude can be changed together, and more suitable injection molding can be performed.

[0013] The injection molding method and the injection molding apparatus of the present invention are designed to injection-mold an optical information recording substrate (product). This makes it possible to mold a high-quality optical information recording substrate such as a magneto-optical disk, digital video disk, or the like free from uneven transfer and insufficient transfer in a short molding cycle.

[0014]

Embodiments of the present invention will be described below. In addition, the injection molding method and apparatus according to the embodiment of the present invention can be applied to molding such as multicolor molding and injection compression molding, and further, a molding material in a fluid state or a rubber-like state from a molding machine is placed in a mold. The present invention can be applied to all types of molding in which a molded product is taken out after press-fitting and shaping into a predetermined shape.

Examples of the molding material used in the present invention include materials having a slight fluidity during molding, such as organic materials such as plastics, inorganic polymers, and ceramics and metal powders using a resin as a binder. [First Embodiment] First, an injection molding method and apparatus for performing molding by changing the amplitude of resonance will be described with reference to FIGS.

The injection molding apparatus Figure 1 shows an injection molding apparatus according to a first embodiment of the present invention. (1) Mold As shown in FIG. 1, as the mold 1 of the apparatus according to the present embodiment, a mold composed of a fixed mold 2 and a movable mold 3 can be used. A cavity 4 is formed on the parting surface of the mold 3. Examples of the material of the mold 1 include metals, ceramics, and graphite.

As shown in FIG. 1, as the fixed mold 2 of the apparatus according to the present embodiment, a general-purpose mold having a sprue 5 on a central shaft can be used. A nozzle 6 of a molding machine (not shown) injects and supplies molding material to the cavity 4 via the sprue 5. It is preferable that the contact surface of the sprue 5 with the nozzle 4 is located substantially at a node (described later) of the ultrasonic vibration (displacement waveform) in the fixed mold 2. The fixed mold 2 is fixed to a fixed mold fixing plate 22 via a fixed mold holding member 21. Here, the fixed mold holding member 21 holds a substantially central outer periphery of the fixed mold 2. In this case, in order to suppress the outflow of the vibration of the fixed mold 2 to the outside, the fixed mold 2 and the fixed mold holding The member 21 is in a holding state by line contact.

Movable Mold As shown in FIG. 1, a movable mold 3 of the apparatus according to the present embodiment is a general-purpose mold which is disposed substantially concentrically with the fixed mold 2 in contact therewith. be able to. The movable mold 3 is also fixed to a movable mold fixing plate 32 via a movable mold holding member 31. Also in this case, the movable mold holding member 31 holds the outer periphery at the substantially center of the movable mold 3 and suppresses the outflow of the vibration of the movable mold 3 to the outside. An anti-vibration material (not shown) is inserted and held therebetween.

As shown in FIG. 2, the mold 1 may have a structure in which a movable mold is divided into two parts and an n-wavelength resonator 9 is provided therein (n = 0.5 mm: positive). integer). In this case, the n-wavelength resonator 9 is disposed inside the movable mold 3, and one end of the movable mold 3, which constitutes a part of the movable mold 3, is connected to the fixed mold 2, the end on the sprue 5 outlet side. The cavity 4 is formed together with the portion. Further, the antinode of the resonance generated from the n-wavelength resonator 9 is matched with the molding position of the cavity 4 and the node of the resonance is fixed at the fixing position of the mold (the convex portion or the concave portion of the resonator (fitting, fixing portion). It is preferable to apply a vibration so as to coincide with ()). As a result, the vibration of the cavity portion 4 is large, and the vibration is small at the fitting and fixing portions, and the energy loss due to the propagation of the vibration to the movable mold 3 can be minimized.

(2) Vibration direction converter As shown in FIG. 1, the resonator of the device according to the present embodiment is an LL type resonator which converts the direction of propagation of vibration from the ultrasonic transducer 8 described later by 90 degrees. Is used. In addition, as the vibration direction converter 7, up and down, left and right,
Vibration may be propagated from any rear position. Therefore, in addition to the above LL type, LL
-L type or RL type can be used.
Further, as the vibration direction converter 7 and the n-wavelength resonator 9,
Usually, a material used as a material of the mold 1 can be used, but it is preferable to use a material having a small transmission loss of ultrasonic waves, for example, a titanium alloy, duralumin or the like.

(3) Ultrasonic oscillator The ultrasonic oscillator 10 is designed and manufactured in advance so that the resonance frequency becomes a frequency that can be tracked by the ultrasonic vibrator 8, so that the nozzle 6 of the molding machine is connected to the sprue 5. Press
When the molding material is supplied to the cavity 4 via the sprue 5, the tracking of the change in the resonance frequency with respect to the instantaneous load change is always performed, and the supply of the required power is also required according to the instantaneous change (less than the maximum output). Can be set to supply.

(4) Molding Material As the molding material used in the present invention, a material having a slight fluidity at the time of molding, such as an organic material such as plastic, an inorganic polymer, a ceramic or a metal powder using a resin as a binder, or the like is used. Can be mentioned. Here, examples of the plastic include α-olefin-based resins (polyethylene, polypropylene, polystyrene, syndiotactic polystyrene, vinyl chloride resin, polybutene, ultrahigh molecular weight polyethylene, polymethylpentene, ionomer,
Such as polybutylene), polyester resin, polyether resin, polycarbonate resin, polyamide resin,
Methacrylic resin, fluorine resin, methacrylate-butadiene-styrene resin, acrylate-acrylonitrile-styrene resin, acrylonitrile-styrene resin, acrylonitrile-butadiene-styrene resin, polyacetal resin, cellulose resin, polyvinylidene chloride, Chlorinated polyethylene, ethylene-vinyl acetate resin, polyurethane resin, silicone resin, allyl resin, furan resin, liquid crystal polymer, epoxy resin, polybutadiene resin, silicone resin, unsaturated polyester resin, amino resin, styrene-butadiene elastomer, Examples thereof include polyester elastomers, polyethylene elastomers, urethane elastomers, and vinyl chloride elastomers.

These resins include additives such as an oxidation stabilizer, a light stabilizer, a light absorber, a colorant, a lubricant, and a release agent;
Fillers and reinforcing agents such as talc, calcium carbonate, glass fiber and carbon fiber can be added as needed. Among them, molded products include optical disks, magneto-optical disks,
Examples of molding materials for molding information recording substrates such as digital video disks include polycarbonate resins, methacrylic resins such as polymethyl methacrylate, and amorphous polyolefin resins, and the application to these molded articles is preferable. .

Injection molding method An injection molding method performed using the injection molding apparatus of the present embodiment is performed as follows. That is, the molding material is supplied from the molding machine to the cavity 4 of the mold via the sprue 5 of the mold 1 and injected. At this time, the ultrasonic vibrator 8 is vibrated by the high-frequency power from the ultrasonic oscillator 10 and the whole or a part of the mold is n-wavelength resonance (n =
(1/2) m, m = positive integer). When the injection molding apparatus shown in FIG. 2 is used, an n-wavelength resonator 9 that resonates by vibration is provided in the movable mold 3, and this also causes n-wavelength resonance by ultrasonic waves.

In these cases, preferably, the antinode of resonance due to vibration coincides with the position of the cavity of the mold, and more preferably, the node of resonance due to vibration coincides with the fixed position of the mold. An injection molding apparatus that performs molding while resonating the whole or a part thereof can be given. The vibration modes of mold resonance include longitudinal vibration, transverse vibration, flexural vibration,
Known vibration modes such as radial vibration and rotational vibration can be used, but a longitudinal vibration mode is preferable in order to uniformly apply ultrasonic vibration to the molding material.

Amplitude The larger the amplitude used in the vibration direction converter 7 shown in FIGS. 1 and 2, the more the effect can be sufficiently exhibited.
It is desirable to set in accordance with the degree of fatigue of the material of the mold.
The amplitude can be changed by controlling the high frequency power of the ultrasonic transmitter. Specifically, mold 1
Maximize resonance amplitude (eg 10μm) when injecting resin into
And minimize the amplitude of resonance during resin cooling (for example, 3 μm)
And This change in the amplitude can be changed continuously or intermittently from the maximum to the minimum (including the amplitude 0). Further, the position of the mold 1 for changing the amplitude may be the whole, or may be a part of the mold 1 such as the cavity 4. However, the maximum amplitude is determined by the output of the transmitter, the shape of the vibrator, and the shape of the mold. In addition, the maximum amplitude has an upper limit depending on the mold material used.
m, and 100 μm for a titanium alloy.

Vibration Frequency The vibration frequency used in the ultrasonic vibrator 8 is preferably 1 [KHz] to 10 [MHz]. In order to make the ultrasonic wave act on the material at the time of molding very effectively, it is 1 [KHz].
0 [KHz] to 100 [KHz] is more preferable.

[Second Embodiment] Next, an injection molding method and apparatus for performing molding by changing the resonance frequency will be described with reference to FIGS.

Injection Molding Apparatus FIGS. 3 and 4 show an injection molding apparatus according to a second embodiment of the present invention. (1) Mold As shown in FIG. 3, the mold 1 of the apparatus in the present embodiment.
Has the same configuration as the mold 1 of the first embodiment shown in FIG.

(2) Vibration direction converter The apparatus according to the present embodiment mounts a plurality of ultrasonic vibrators 81, 82 and 83 as shown in FIGS. Although the direction changing member 7 is used, other conditions are the same as those of the first embodiment shown in FIG.

(3) Ultrasonic Vibrator In the apparatus of this embodiment, three ultrasonic vibrators 81, 82, 83 having different fundamental frequencies are connected to the upper part of the vibrating direction converter 7,
It is connected to the lower part and one side part, respectively. Where,
The fundamental frequencies of the lower and one side ultrasonic transducers 81, 82 and 83 are 15 KHz, 19 KHz and 23 K, respectively.
Hz. Depending on the molding conditions, the number of ultrasonic transducers having different fundamental frequencies can be two, or four or more.

(4) Ultrasonic Oscillator The ultrasonic oscillator 10 used in the apparatus of the present embodiment is the same as that of the first embodiment. However, in the present embodiment, the high-frequency power from the ultrasonic oscillator 10 is used. The signal from the molding machine is selectively supplied to any one of the ultrasonic vibrators via a switching means (not shown) such as a timer which takes in the signal.

Injection molding method The injection molding method performed using the injection molding machine of the present embodiment is as follows.
Except for different conditions for the frequency and amplitude of the resonance,
This is the same as the injection molding method of the first embodiment shown in FIG. The material to be molded is the same as that of the first embodiment. Vibration frequency At the time of injection, for example, a lower ultrasonic vibrator 82 is selected from the plurality of ultrasonic vibrators 81, 82, 83, and high-frequency power is supplied to the ultrasonic vibrator 82 from the ultrasonic oscillator 10,
At the time of cooling, the high frequency power is supplied by switching from the lower ultrasonic transducer 82 to the upper ultrasonic transducer 81. Thus, the frequency of resonance is 19 KHz during injection and 15 KHz during cooling. At this time, it is preferable that the selected ultrasonic transducer has a fundamental frequency as close as possible. The frequency to be used is determined by the size and material of the mold. For example, when a mold made of duralumin (sound speed 5100 m / sec) with an outer diameter of 150 is used, 17 is used.
KHz (5100 m / sec) / 150 (mm) / 2 =
It is preferable to use a frequency near 17000 (1 / sec) = 17 KHz).

In the case of the second embodiment, too, the larger the amplitude, the more the effect of the ultrasonic wave can be sufficiently exhibited. In this case, too, it is preferable to set the amplitude in accordance with the fatigue strength of the material of the mold used. When the mold is duralumin, the thickness is 40 μm.

The amplitude can be changed by controlling the high-frequency power supplied to one ultrasonic transducer selected from a plurality of ultrasonic transducers. In this manner, during one cycle of molding, it is possible to cause the frequency change of the resonance in the second embodiment and the amplitude change of the resonance in the first embodiment to be performed together, and injection molding can be performed under more favorable conditions. I can do it.

[Embodiment 1] The injection molding apparatus shown in FIG.
The VD-ROM stamper was attached, injection molding was performed under the following conditions, and the results of evaluating the molding cycle are shown in Table 1. (1) Ultrasonic frequency: 19 KHz (oscillator: SONOPET 12000 manufactured by Seidensha Electronics Co., Ltd.) (2) Resonance mold: 1.5-wavelength resonator (4) Molding material: polycarbonate (Tufflon MD15
00) (5) Molded product: disk (optical disk) with a diameter of 120 and a thickness of 0.6 mm

[Comparative Example 1] The amplitude during injection and during cooling was
Table 1 shows the results of evaluating the molding cycle under the same conditions as in Example 1 except that both were fixed at 10 μm.

[0038]

[Table 1]

[Embodiment 2] The injection molding apparatus shown in FIG.
The VD-ROM stamper was attached, injection molding was performed under the following conditions, and the results of evaluating the transferability are shown in Table 2. (1) Ultrasonic frequency: 15 KHz for injection, 19 KHz for holding pressure, 19 KHz for cooling (in this case, the vibration distribution of the parting surface was as shown in FIG. 5) (2) Resonant mold: 1.5-wavelength resonator ( 3) Amplitude: 5 μm (4) Molding material: Polycarbonate (Tufflon MD1500) (5) Molded product: Disk 120 mm in diameter and 0.6 mm thick (optical disk)

Comparative Example 2 Table 2 shows the results of evaluation of the transferability under the same conditions as in Example 2 except that the frequency at the time of injection and the frequency at the time of cooling were both constant at 19 KHz.

[0041]

[Table 2]

In the second embodiment, the vibration distribution of the parting surface is controlled during the molding while changing the frequency of the ultrasonic wave.
Since the vibration distribution was changed in accordance with the flow or cooling of the resin, uneven transfer and insufficient transfer of the inner and outer circumferences could be suppressed.

[0043]

Since the amplitude or frequency of resonance or the amplitude and frequency can be controlled during injection molding, the molding cycle can be shortened, uneven transfer and insufficient transfer can be eliminated, and a high quality molded article can be obtained. Play.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing an example of an injection molding apparatus according to a first embodiment of the present invention.

FIG. 2 is a partial sectional view showing another example of the injection molding apparatus according to the first embodiment of the present invention.

FIG. 3 is a partial sectional view showing an example of an injection molding apparatus according to a second embodiment of the present invention.

4 is a perspective view of an ultrasonic transducer and a vibration direction converter of the injection molding apparatus shown in FIG.

FIG. 5 is a diagram illustrating a vibration distribution on a parting surface according to a second embodiment.

[Explanation of symbols]

 Reference Signs List 1 mold 2, 2 'fixed mold 3, 3' movable mold 4 cavity 5 sprue 6 nozzle 7 vibration direction converter 8 (81, 82, 83) ultrasonic transducer 9 n-wavelength resonator 10 ultrasonic oscillator

Claims (8)

[Claims] 1. A method for performing injection molding while resonating the whole or a part of a mold by ultrasonic vibration, wherein the injection molding is performed while changing resonance conditions of the mold. 2. The injection molding method according to claim 1, wherein the resonance condition is a resonance amplitude. 3. The injection molding method according to claim 1, wherein the resonance condition is a resonance frequency. 4. The injection molding method according to claim 2, wherein the amplitude of the resonance is maximized when the resin is injected into the mold and minimized when the resin is cooled. 5. The injection molding method according to claim 3, wherein the resonance frequency is maximized when the resin is injected into the mold, and is minimized when the resin is cooled. 6. The injection molding method according to claim 1, wherein the product to be injection molded is an optical information recording substrate. 7. An apparatus for performing injection molding while resonating the whole or a part of a mold by ultrasonic vibration, comprising: an ultrasonic vibrator for converting high-frequency power from an ultrasonic oscillator into vibration; and an ultrasonic vibrator. An injection molding apparatus, comprising: a vibration direction conversion body that couples a mold and the mold; and controlling the high-frequency power of the ultrasonic oscillator to change the amplitude of the resonance. 8. An apparatus for performing injection molding while resonating the whole or a part of a mold by ultrasonic vibration, comprising: a plurality of ultrasonic vibrators having different fundamental frequencies for converting high-frequency power from an ultrasonic oscillator into vibration; Having a vibration direction converter that couples the plurality of ultrasonic transducers and the mold, and selectively applying high-frequency power to the ultrasonic transducers from the ultrasonic oscillator to obtain a resonance frequency. An injection molding apparatus characterized by changing the temperature.