JP3525586B2 - Injection molding method for optical products - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an injection molding method. More specifically, it relates to an injection molding method particularly useful for molding optical products such as magneto-optical disks and digital video disks.

[0002]

2. Description of the Related Art In recording media such as magneto-optical discs and digital video discs, higher densification (increasing recording density) is being advanced, but it is difficult to satisfy the current molding method sufficiently. However, there are problems such as a decrease in transferability, optical distortion, and warpage due to residual stress.

As a method of improving the fluidity of the molding material and eliminating such a defective phenomenon, a method of applying ultrasonic vibration to the gate portion and cavity of the mold to improve the fluidity of the molding material ( JP-B-57-2088, JP-A-5
JP-A-8-134722, JP-A-62-135333, JP-A-62-135334, JP-A-62-249717, and JP-A-2-47026) are disclosed.

[0004]

However, in these methods, the mold structure must be very complicated, and ultrasonic vibrations adversely affect the mold itself and other parts of the apparatus. There is a problem and a problem that ultrasonic vibration cannot be sufficiently applied to the molding material.

The present invention has been made in view of the above-mentioned problems, and an injection molding method capable of dramatically improving the fluidity of a molding material and preventing a defective phenomenon occurring when a molded article is formed. The purpose is to provide.

[0006]

[Means for Solving the Problems] In order to achieve the above object, as a result of intensive research, as a result of not only simply applying ultrasonic vibrations to a mold, but also resonating the whole or a part of the mold, The fluidity is dramatically improved and the skin layer is reduced by filling the molding material at high speed,
The inventors have found that it is possible to prevent a defective phenomenon that occurs when a molded product is molded, and have completed the present invention.

That is, according to the present invention, polycarbonate
In the injection molding method, in which a molding material that is a resin based resin is supplied to the cavity of the mold and injection molding is performed, the whole or a part of the mold has a vibration frequency of 1 [KHz] to 10 [MHz].
In while resonated by vibration, 150 ^[cm 3 / se
c] The magneto-optical characteristic of molding at an injection rate of
An injection molding method for a disc and a digital video disc is provided.

As a preferred embodiment thereof, a magneto-optical disk and a digital bidet characterized in that an abdominal part of the resonance caused by the vibration is aligned with the position of the cavity of the mold.
An injection molding method for Odisk is provided.

Further, as a preferred embodiment thereof, the node portion of the resonance caused by the vibration is made to coincide with the fixed position of the mold, and the magneto-optical disk and the digital video disc.
A method of injection molding a disc is provided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the injection molding method of the present invention will be specifically described below. The present invention is characterized in that a molding material is supplied to a cavity of a mold, and molding is performed at an injection rate of 150 [cm ³ / sec] or more while resonating the whole or part of the mold by vibration.

The injection molding method of the present invention includes a multicolor molding method, an injection compression molding method, and the like. Furthermore, a molding material in a fluidized state or a rubber-like state from a molding machine is press-fitted into a mold, and a predetermined amount is obtained. It includes all molding methods in which a molded product is taken out after being shaped into the above shape.

1. Injection Rate In the present invention, the injection rate refers to the volume of resin injected from a nozzle of an injection molding machine per unit time. In the present invention, an injection rate of 150 [cm ³ / sec] or more is used. If it is less than 150 [cm ³ / sec], the molding material is rapidly cooled in the mold, the flow pressure loss increases, and the generation of the skin layer (orientation layer) increases. This causes a defective phenomenon such as distortion of the molded product.

2. Mold Resonance In the present invention, as a device for realizing the mold resonance,
For example, a device that supplies a molding material from a molding machine to a cavity of a mold through a sprue of the mold and injects the same, is equipped with an ultrasonic vibrator,
Wavelength resonance (n = (1/2) m, m: positive integer) or a resonator that resonates by vibration is provided in the movable mold, and this is caused to resonate for n wavelengths by ultrasonic waves. The abdomen of resonance due to vibration is made to coincide with the position of the cavity of the mold, and more preferably, the node of resonance due to the vibration is made to coincide with the fixed position of the mold, and the whole or part of the mold is resonated while molding. An injection molding device that performs The vibration modes of the mold resonance are longitudinal vibration,
Known vibration modes such as lateral vibration, flexural vibration, radial vibration, and rotational vibration can be used, but the longitudinal vibration mode is preferable in order to uniformly apply ultrasonic vibration to the molding material.
The present invention will be described below with reference to the apparatus used in the embodiments of the present invention shown in FIGS.

(1) Mold As shown in FIGS. 1 and 5, as the mold of the apparatus used in the present invention, a mold composed of a fixed mold 3 and a movable mold 4 can be used. Examples of the material include metals, ceramics, graphite and the like.

Fixed Mold As shown in FIGS. 1 and 5, the fixed mold of the apparatus used in the present invention may be a general-purpose fixed mold having a sprue on its central axis.

Movable Mold As shown in FIGS. 1 and 5, the movable mold of the apparatus used in the present invention has a general-purpose structure which is arranged so as to come into contact with the fixed mold substantially concentrically. I can list things. As shown in FIG. 1, the movable mold 4 is preferably divided into two parts for the convenience of temperature control of the mold and for incorporating the resonator 9 into the mold 4, and a convex portion of the resonator 9 or In order to fit and fix the concave portion, it is more preferable to provide a concave portion or a convex portion on the inner peripheral portion of the divided portion. The concave portion or the convex portion is not particularly limited as long as it can be fitted appropriately with the convex portion or the concave portion of the resonator 9.

As shown in FIG. 1, when this fitting and fixing portion uses a resonator, for example, an n-wavelength resonator 9 and an L-L converter 8, an n generated therefrom is used.
It is possible to prevent the vibration from being transmitted to the movable mold 4 and to arrange the resonator in the resonance state by disposing it so as to coincide with the node portion of the wavelength resonance (n = 1/2 m, m is a positive integer). It is preferable because the n wavelengths can be resonated without being disturbed.

(2) Resonator As shown in FIG. 1, the n-wavelength resonator 9 is composed of the movable mold 4
Of the fixed mold 4 and the end of the fixed mold 4 on the outlet side of the sprue 5 form a cavity 6.

Further, as shown in FIG. 1, the resonator is provided with a convex portion or a concave portion on its outer peripheral portion so as to correspond to the concave portion or the convex portion provided on the movable mold 4, and are fitted and fixed to each other. It is preferable. In addition, the antinode of resonance generated from the resonator 9 is made to coincide with the formation position of the cavity 6, and the node of resonance is fixed to the mold (convex portion or concave portion (fitting or fixing portion) of the resonator). It is preferable to apply vibration so as to match with. As a result, the vibration of the cavity 6 is large, and the vibration at the fitting and fixing portions is small, and the energy loss due to the vibration propagation to the movable mold 4 can be minimized.

N-Wavelength Resonator As shown in FIG. 1, the n-wavelength resonator 9 has an n-wavelength (n = 1/2) due to vibration generated from an ultrasonic transducer 7 described later.
m and m are positive integers, and the number of nodes is as small as possible in order to fit the movable mold 4 and to make the fixed part coincide with the resonance node.
<3 is preferable. ) Resonates with. The shape shown in FIG. 1 is a stepped cylindrical shape.

L-L Converter The L-L converter 8 shown in FIGS. 1 and 5 converts the propagation direction of the vibration from the ultrasonic transducer 7 by 90 degrees. This allows the vibrator to be mounted in the vertical direction or in the rear.

The n-wavelength resonator 9 and the L-L converter 8 are made of a material having a small ultrasonic transmission loss, such as a titanium alloy.
It is preferable to use duralumin or the like.

(3) Ultrasonic device Since the ultrasonic oscillator is designed and manufactured in advance so that the resonance frequency of the resonator 9 can be tracked by the ultrasonic oscillator 7, the nozzle 1 of the molding machine is The sprue 5 is pressed into contact with the cavity 6, and when the molding material is supplied to the cavity 6 through the sprue 5, the resonance frequency is constantly tracked against changes in the load, and the necessary power is also supplied according to the changes. It can be set to deliver a quantity (less than maximum output).

Vibration Frequency As shown in FIGS. 1 and 5, the vibration frequency used in the ultrasonic transducer 7 is 1 [KHz] to 10 [MH].
z] is preferable, and 10 [KHz] to 100 [KH] in order to make the ultrasonic waves act extremely effectively on the material during molding.
z] is more preferable.

Amplitude The amplitude used in the ultrasonic transducer 7 is preferably large, so that the effect can be sufficiently exhibited, so it is desirable to set it in accordance with the degree of fatigue of the material of the mold.

Ultrasonic wave application time The ultrasonic vibration is generated in the ultrasonic vibrator 7 depending on the intended effect, either during injection only, during pressure holding only, or both injection and pressure holding times. You can choose.

3. Molding Material Examples of the molding material used in the present invention include organic materials such as plastics, inorganic polymers, ceramics using a resin as a binder, metal powders, and the like, which have some fluidity during molding. Here, as the plastic, for example, α-olefin resin (polyethylene, polypropylene, polystyrene, syndiotactic polystyrene, vinyl chloride resin, polybutene, ultra high molecular weight polyethylene, polymethylpentene, ionomer,
Polybutylene etc.), 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 crystalline 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.

[0028]

EXAMPLES The present invention will be described in more detail below with reference to examples. [Embodiment 1] In the apparatus used in the present embodiment shown in FIG. 1, a fixed mold 3 made of duralumin 2024 having a sprue 5 in its central axis portion is movable to a movable part made of duralumin 2024. The mold 4 was disposed so as to abut substantially concentrically. In this case, the fixed mold 3 is the fixed mold fixing plate 2, and the movable mold 4 is the movable mold fixing plate 1.
Fixed by 0 respectively. The movable mold 10
An n-wavelength resonator 9 and an L-L converter 8 are provided as a resonator inside. Further, as shown in FIG. 2, a cavity 6 having a circular shape, an outer diameter of 130 mm, and a thickness of 0.5 mm is formed by one end of the fixed mold 3 and one end of the n-wavelength resonator 9. is doing. Further, a concave portion is formed on the inner peripheral portion of the divided portion of the movable mold 4, and the concave portion and the n-wavelength resonator 9 are formed.
The convex portion formed on the outer peripheral portion of was fitted and fixed. Also L-
An ultrasonic transducer 7 (made by Seidensha Denshi Kogyo Co., Ltd.) is used as the L converter 8.
SONOPET 1200B; fundamental frequency 19.15KH
z) was joined. Further, the projecting pin 11 fixed to the movable mold fixing plate 10 is movably arranged by the hydraulic cylinder 12 in order to project and take out the molded product molded in the cavity 6. A nozzle 1 of a molding machine (not shown) is disposed in contact with the inlet of the sprue 5 of the fixed mold 3. Polycarbonate (Panlite AD-5503M manufactured by Teijin Chemicals Ltd.) was used as a molding material in such an injection molding apparatus, and injection molding was performed under the following conditions. Mold clamping force 50 [ton] Injection rate 250 [cm ³ / sec] Injection pressure 1,500 [Kgf / cm ² ] Resin temperature 320 [° C] Mold temperature 120 [° C] Amplitude 10 [μm] Resonance Shown in FIG. 1-wavelength resonance cavity part The molded product obtained by plating with hard chrome did not show a defect phenomenon in appearance. Also, measure the birefringence at a distance from the center of the molded product,
The results are shown in Fig. 4, and the birefringence was extremely low at any distance.

[Comparative Example 1] The same procedure as in Example 1 was carried out except that the injection rate in Example 1 was 70 [cm ³ / sec]. The results of birefringence measurement are shown in FIG.

[Embodiment 2] In Embodiment 1, the injection molding apparatus shown in FIG. 5 was used (projecting pins are not shown), and 20 concave portions of 5 μm were formed on the cavity surface of the cavity 6. Processing and resonance are shown in FIG.
The molding conditions were the same as in Example 1 except that the five-wavelength resonance was used, that is, the molding material, the mold material, the cavity shape, the ultrasonic oscillator, and the resonance. Figure 4 shows the result of birefringence measurement.
Table 1 shows the results of the transferability measurement. The transferability means (the height of the convex portion of the molded product / the height of the concave portion of the surface of the resonator of the cavity 6 (5 μm)) × 100 [%], and the average value of 20 points was used.

[Comparative Example 2] The same procedure as in Example 2 was carried out except that ultrasonic waves were not applied. Table 1 shows the results of measurement of transferability.

[0032]

[Table 1]

[0033]

As described above, according to the present invention, defective phenomena such as transfer unevenness and optical distortion of a molded product can be reduced. That is, since the friction between the inner surface of the mold and the resin is reduced by the ultrasonic vibration, the fluidity of the molding material is improved, and the occurrence of the defective phenomenon can be prevented. Further, by filling the molding material at a high speed, it is possible to reduce the formation of the skin layer during the cooling and solidification process of the molded product in the mold, so that the occurrence of defective phenomena such as warpage and optical distortion due to residual strain. Can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view schematically showing an injection molding device used in an embodiment of the present invention.

FIG. 2 is a front view schematically showing the shape of the cavity of the injection molding apparatus used in the example of the present invention.

FIG. 3 is an explanatory view schematically showing a state of resonance (one-wavelength resonance) of the n-wavelength resonator and the L-L converter of the injection molding apparatus in the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing the relationship between the distance from the center of a molded article and birefringence obtained by Examples and Comparative Examples of the injection molding apparatus and the injection molding method using the same according to the present invention.

FIG. 5 is a schematic sectional view schematically showing an injection molding apparatus used in another embodiment of the present invention.

FIG. 6 is an n of an injection molding apparatus according to another embodiment of the present invention.
It is explanatory drawing which shows typically the state of resonance (1.5 wavelength) of a wavelength resonator and an L-L converter.

[Explanation of symbols]

1 nozzle 2 Fixed mold fixing plate 2'fixed die holding member 3 fixed mold 4 movable mold 5 sprues 6 cavities 7 Ultrasonic transducer 8 L-L converter 9 n wavelength resonator 10 Movable mold fixing plate 10 'Movable mold holding member 11 protruding pin 12 hydraulic cylinder

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-3-213317 (JP, A) JP-A-3-213318 (JP, A) JP-A-7-68586 (JP, A) JP-A-7- 80899 (JP, A) JP 3-213319 (JP, A) JP 5-329866 (JP, A) JP 2-131910 (JP, A) JP 5-104598 (JP, A) JP-A-6-270188 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29C 45/46 B29C 45/26 B29C 45/77

Claims (3)

(57) [Claims] 1. A molding material is a polycarbonate resin was supplied into the mold cavity, the injection molding method of performing injection molding, the whole or part of the mold, the vibration frequency 1
A magneto-optical disk and a digital bidet characterized by performing molding at an injection rate of 150 [cm ³ / sec] or more while resonating by vibration at [KHz] to 10 [MHz].
Odisk injection molding method. 2. An abdomen of the resonance caused by the vibration is aligned with the position of the cavity of the mold.
Ejection molding method of the magneto-optical disk and digital video disk described. 3. The node portion of resonance due to the vibration is made to coincide with a fixed position of a mold.
Ejection molding method of the magneto-optical disk and digital video disk described.