JP3779128B2 - Ultrasonic injection mold for optical disc - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic injection mold for an optical disc, and more particularly to an ultrasonic injection mold for an optical disc that has excellent transferability and can effectively prevent the occurrence of birefringence and warpage.
[0002]
[Prior art]
Optical discs such as CD and DVD are arranged at the bottom of a movable mold, a fixed mold, a circular cavity for forming a disk formed on the contact surface of the movable mold and the fixed mold, and the cavity. A molten resin such as polycarbonate is injected into a mold having a stamper for forming irregularities (pits) on the surface of the disk.
[0003]
When thin-walled products are obtained by injection molding like the above-mentioned optical discs, the fluidity of the molten resin in the cavities is improved to prevent filling unevenness and the occurrence of defects such as shrinkage deformation and birefringence. There is a need to prevent. In order to prevent the occurrence of such defects, for example, in the injection molding method disclosed in Japanese Patent Laid-Open No. 10-661, the relationship between the equivalent diameter (D) of the mold and the wavelength (λ) of the ultrasonic vibration is D < Injection molding is performed so as to be 0.6λ.
[0004]
However, since the conventional ultrasonic molding method described above uses only longitudinal vibration, the diameter (usually about 210 mm) of the surface (contact surface between the fixed mold and the movable mold) on which the cavity of the optical disk molding mold is formed. ) Is ½ or more of the resonance wavelength (λ) of the ultrasonic wave (for example, in the case of a SUS mold, 130 mm or more at a frequency of 19 KHz), vibration transmitted in the radial direction is generated. For this reason, there is a problem that it is difficult to hold the mold and the nozzle because the fixed part of the mold and the mounting part of the nozzle cannot be matched with the vibration “node” (the point where the amplitude becomes 0).
[0005]
In addition, since the conventional ultrasonic molding mold structure uses only longitudinal vibration, the entire movable mold and fixed mold must have a thickness of at least one wavelength, and the vibration direction can be changed. When the body is included, the entire thickness becomes 400 mm or more, so that there is a problem that it cannot be attached between the die plates of the production machine (30 ton injection molding machine).
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and in an ultrasonic injection mold for optical discs for injection molding of optical discs, the amplitude of ultrasonic waves transmitted in the radial direction of the cavity is minimized. It is an object of the present invention to provide an ultrasonic injection mold for optical discs that can maintain a good transferability and can hold a mold and a nozzle well between die plates while preventing the occurrence of birefringence and shrinkage deformation. And
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, an ultrasonic injection mold for optical discs according to the present invention comprises a movable mold, a fixed mold, and a disk molding formed on a contact surface of the movable mold and the fixed mold. A cavity and the surface of the disk placed at the bottom of the cavity Unevenness An ultrasonic injection mold for an optical disc, comprising: a stamper for forming the ultrasonic wave; and an ultrasonic wave generating means attached to the movable mold or the fixed mold to apply ultrasonic waves to the cavity during injection molding. And it is set as the structure which formed one or several slits in the direction which cross | intersects the radial direction of the said cavity in the area | region in which the said cavity of the said movable mold and the fixed mold was formed.
Since the thickness of the portion is reduced by forming the slit, vibration is suppressed at the portion. Therefore, the amplitude of vibration transmitted in the radial direction of the cavity can be reduced.
[0008]
The slit is an ultrasonic wave input to the movable mold or the fixed mold when the wavelength of the ultrasonic wave whose transmission direction is changed inside the movable mold or the fixed mold is λ. It may be formed at a position of nλ / 4 (n = 1, 3, 5,...) From the sound wave input portion. Here, the “ultrasonic input section” refers to a portion where the ultrasonic wave generating means or the vibration direction change body and the movable mold or the fixed mold are in contact with each other.
The resonance amplitude of vibration becomes a node at nλ / 4 (n = 1, 3, 5,...). By forming a slit at this position, the amplitude of vibration transmitted in the radial direction can be minimized.
[0009]
Particularly in a large-diameter mold, a plurality of rows may be formed inward from the outer peripheral edge of the cavity along the radial direction of the cavity. Also in this case, the amplitude of vibration transmitted in the radial direction can be further reduced by providing at a position where the amplitude of resonance becomes a node, that is, nλ / 4 (n = 1, 3, 5,...). .
[0010]
The ultrasonic wave generation means may be provided at an input end of a vibration direction changer whose output end is connected to the ultrasonic wave input portion of the movable mold or the fixed mold. The vibration direction change body may be any of LL type, LLL type, and RL type. By using the vibration direction changer, it is possible to amplify the input vibration and output it to the mold, and it is possible to improve the fluidity by giving a longitudinal vibration having a larger amplitude to the cavity.
[0011]
Furthermore, the movable mold and the vibration direction change body or the fixed mold may be provided with product release means for releasing the injection molded product from the cavity. As the mold release means, a protruding pin that protrudes into the cavity when the mold is opened is generally used. By using such a product release means, it is possible to reliably release the molded product from the mold.
[0012]
In particular, if the mold release means is configured to release the product from the cavity by vibrating the movable mold having the stamper or the fixed mold, it is necessary to form a taper in the unevenness of the stamper. As a result, the unevenness can be formed with high density, and a disk capable of recording a large amount of information can be formed.
[0013]
In addition, it is preferable to guide the movable mold and the fixed mold at the time of mold clamping or mold opening by inlay-type guide means.
As a guide for the mold when opening and closing the mold, there are a guide post system in which a guide post provided on one side of the mold is inserted into a guide post provided on one side of the mold and a conical shape provided on one side of the mold. There is an inlay method in which a conical pin provided on the other side of the mold is fitted into the hole of the mold, but the inventor of the present application conducted a comparative experiment between the guide post method and the inlay method, It was found that the effect of suppressing vibration at the nozzle joint on the fixed mold side was greater.
[0014]
Further, it is preferable that the ultrasonic wave generating means generates a transverse vibration or a radial vibration transmitted in the radial direction of the cavity in addition to the longitudinal vibration in the whole of the fixed mold and the movable mold. .
In addition to longitudinal vibration, lateral vibration or vibration transmitted in the radial direction of the cavity is added, and the vibration is compounded, so that the thickness of the movable mold and fixed mold is compared with that using only longitudinal vibration. Less than half.
Further, the movable mold and the vibration direction change body or the fixed mold may be provided with punch means for punching (punching) a predetermined portion of the injection-molded product. You may comprise the product release means to protrude.
[0015]
In addition, it is good to insert a support member in the said slit, and to make it support the bottom part of the said slit at the end of the said support member at the time of injection molding. In this case, the width t of the gap between the support member and the inner wall of the slit may be in the range of 0.1 mm <t <0.3 mm.
The other end of the support member may be attached to a fixed mold fixing member for fixing the fixed mold or a movable mold fixing member for fixing the movable mold. An attachment member may be provided in the vicinity of the mold, and the support member may be attached to the attachment member.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the ultrasonic injection mold for optical disc of the present invention will be described in detail with reference to the drawings.
In addition, this invention is not limited at all by the following embodiment, It can change variously within the scope of the present invention.
[0017]
[First Embodiment]
FIG. 1 is a side view of a part of an ultrasonic injection mold for an optical disc according to a first embodiment of the present invention, and FIG. 2 shows a displacement waveform of vibration transmitted in the mold of FIG. It is a figure explaining.
[0018]
[Injection molding machine]
In the injection molding machine to which the ultrasonic injection mold for optical disc of the present invention is applied, a molten resin is press-fitted into the mold, and the resin is molded into a shape corresponding to the cavity shape and taken out from the mold. All optical disk ultrasonic injection molding machines are included.
In the injection molding machine of this embodiment, the fixed mold 3 and the movable mold 4 described in detail below are first clamped in an unloaded state, and then the molten resin is injected into the cavity 6 from the nozzle 1 at a high pressure. Thus, the fixed mold 3 and the movable mold 4 are slightly opened.
Thereafter, compression molding is performed while applying a clamping pressure to the movable mold 4, and the molded product is taken out after cooling. Ultrasonic waves are applied during the period from the start of resin injection to cooling and during mold release after mold opening.
[0019]
[Mold]
As shown in FIG. 1, the ultrasonic injection mold for an optical disk according to this embodiment includes a fixed mold 3 having a sprue 5 on a central axis X, and a movable mold disposed to face the fixed mold 3. And a mold 4.
[0020]
The fixed mold 3 is fixed to the fixed mold fixing plate 2 by a fixed mold holding member 13, and the movable mold 4 is fixed to the movable mold fixing plate 9 by a movable mold holding member 10.
The movable mold fixing plate 9 is attached to the tip of the piston rod of the hydraulic cylinder 11 and moves the movable mold 4 forward and backward with respect to the fixed mold 3 as the piston rod moves forward and backward. The movable mold 4 is clamped and opened.
[0021]
A circular cavity 6 for forming an optical disk is formed on the contact surfaces 3a and 4a where the fixed mold 3 and the movable mold 4 abut. A stamper 15 for forming irregularities (pits) on the surface of the optical disk is disposed at the bottom of the cavity 6 on the movable mold 4 side. A cooling water passage 16 is formed around the cavity 6 inside the fixed mold 3 and the movable mold 4.
[0022]
[Form of outer peripheral edge of mold]
On the outer peripheral edges of the fixed mold 3 and the movable mold 4, stepped portions 3 b and 4 b each having a reduced thickness in the thickness direction (direction parallel to the X axis) are formed. Here, the relationship between the cross-sectional area of the stepped portions 3b and 4b and the cross-sectional area of the portion where the stepped portions 3b and 4b are not formed is preferably as follows.
That is, II-II passing through a portion not forming the stepped portions 3b, 4b with respect to a cross-sectional area of a portion cut along the line II, I'-I 'passing through the stepped portions 3b, 4b, It is preferable that the cross-sectional area of the section taken along the line II′-II ′ is formed so as to be in the range of 0.85 to 0.95 times.
[0023]
Flange portions 3c and 4c are further formed on the outer peripheral side of the stepped portions 3b and 4b. The flange portions 3c and 4c are fixed portions for fixing the fixed mold 3 and the movable mold 4 to the fixed mold fixed plate 2 and the movable mold fixed plate 9, respectively. In the stepped portions 3b and 4b, the amplitude of vibration transmitted in the radial direction of the cavity 6 becomes a node. Therefore, it is preferable to make the thickness of the flange portions 3c and 4c provided on the outer peripheral side as thin as possible. In consideration of the pressure applied to the flange portions 3c and 4c at the time of mold clamping, the thickness is preferably 5 mm to 10 mm. Further, in order to reduce the pressure shared by the flange portions 3c, 4c as much as possible, the movable mold holding member 10 and the fixed mold holding member 13 are provided not only on the flange portions 3c, 4c but also on the stepped portions 3b, 4b. It is preferable to abut.
[0024]
[slit]
In the fixed mold 3 and the movable mold 4, a slit 20 is formed from the surface facing the fixed mold fixed plate 2 and the movable mold fixed plate 9 toward the cavity 6. The slit 20 is formed on the circumference in the radial region L (see FIG. 2) of the fixed mold 3 and the movable mold 4 in which the cavity 6 is formed.
The slit 20 is on the X axis passing through a portion where the vibration wave transmitted in the radial direction of the cavity 6 becomes a node, that is, a portion where the vibration direction change body 8 and the movable mold 4 are in contact (ultrasonic input portion). It is preferably formed at a position nλ / 4 (n = 1, 3, 5...) In the radial direction of the cavity 6 from the center of the cavity 6 and closest to the outer peripheral edge of the cavity 6. If the slit 20 is formed at this position, the maximum vibration suppressing effect can be obtained.
[0025]
The radial width W of the cavity 6 of the slit 20 is preferably 10 mm or less, and is set to such an extent that the opposed opening edge of the slit 20 does not contact when vibration is applied to the molds 3, 4, specifically 0.1 mm or more. Is preferred. The depth of the slit 20 is preferably about half of the thickness of the molds 3 and 4.
[0026]
The shape of the slit 20 and how it is arranged in the fixed mold 3 and the movable mold 4 are arbitrary. FIG. 3 is a plan view of a mold showing the shape and arrangement of the slits 20.
In the example shown in FIG. 3A, the single slit 20 is formed in an annular shape concentric with the cavity 6.
In the example shown in FIG. 3 (b), a plurality of slits 20 formed by equally dividing the circumference are arranged along the concentric circle of the cavity 6.
In the example shown in FIG. 3C, the plurality of slits 20 are arranged in two rows along concentric circles having different radii nλ / 4 (n = 1, 3, 5,...).
In the example shown in FIG. 3C, the innermost slit 20 is formed along the concentric circle of the cavity 6 having a radius of nλ / 4 (n = 1, 3, 5,...). It is preferable.
[0027]
The cross-sectional shape of the slit 20 is preferably selected as appropriate according to the amplitude of vibration and the metal forming the dies 3 and 4. As shown in FIG. 4A, the cross-sectional shape of the slit 20 may be formed in an upward U-shape, but the stress is not concentrated at the corner of the bottom of the slit 20 as shown in FIG. It is preferable to form in a U shape as shown. Moreover, as shown in FIG.4 (c), you may give the inclination to the wall surface which the slit 20 opposes.
[0028]
A nozzle 1 that supplies molten resin to the cavity 6 is connected to the inlet of the sprue 5 of the fixed mold 3. Examples of the resin injected from the nozzle 1 include an amorphous thermoplastic resin of an optical system such as polycarbonate, polymethyl methacrylate, and amorphous polyolefin used for the production of an optical disk.
[0029]
[Guide method when opening and closing the mold]
When performing injection molding, it is necessary to accurately position the fixed mold 3 and the movable mold 4 relative to each other. In order to accurately move the movable mold 4 with respect to the fixed mold 3 at the time of clamping, a guide post (or a guide hole) provided on either the fixed mold 3 or the movable mold 4; Either a guide post type guide means provided on the other of the fixed mold 3 or the movable mold 4 and a guide pin inserted through the guide post, and either the fixed mold 3 or the movable mold 4 There is an inlay type in which a conical pin provided in the other of the fixed mold 3 or the movable mold 4 is fitted into the provided conical hole.
[0030]
As will be described later, the present inventor conducted an experiment to determine which of the guide post method and the inlay method has a greater vibration suppressing effect. As a result, it was found that the inlay type guide means is superior in the vibration suppressing effect at the nozzle connection portion on the fixed mold side. Therefore, in the mold of this embodiment, a convex part 17 having a trapezoidal cross section is continuously formed on the contact surface 4a of the movable mold 4 along the circumference surrounding the cavity 6, and the convex part 17 is fitted. A recess 18 having a trapezoidal cross section is formed on the contact surface 3 a of the fixed mold 3.
[0031]
Although the maximum width of the tip of the convex portion 17 (the portion where the convex portion 17 protrudes from the contact surface 4a) can be about 10 mm, the vibration amplitude of the portion where the nozzle 1 contacts the fixed mold 3 is reduced. Therefore, it is preferable to make the width of the tip as small as possible, and it is preferable to set it to about 4 to 5 mm.
The convex portion 17 can be provided at an arbitrary position as long as it is outside the cavity 6. Moreover, it is good also as what provides a convex part in any one of the fixed metal mold | die 3 and the movable metal mold | die 4, and provides a recessed part in the other.
[0032]
[Vibration direction changer and vibrator]
On the surface of the movable mold 4 facing the hydraulic cylinder 11, a vibration direction changer 8 is attached on the central axis X. The vibration direction change body 8 can orthogonally transform the vibration input from the vibration input surface and output it from the vibration output surface. Of the two vibrating bodies 8a and 8b constituting the vibration direction changing body 8, a vibrator 7 as a vibration generating source is attached to the end face of one vibrating body 8a orthogonal to the central axis X, and is parallel to the central axis X. The end face of the vibrating body 8 b is in contact with the movable mold 4. In the vibration direction change body 8, it is preferable to form the output-side vibration body 8b slightly longer than the input-side vibration body 8a. By doing so, it becomes possible to amplify the input vibration from the vibrating body 8a and output it from the end face of the vibrating body 8b.
[0033]
In addition, the vibration direction change body 8 may be any multidimensional vibration direction change body of an LL converter, an LLL converter, and an RL converter. The output of the vibrator 7 is preferably about 1.2 Kw. However, when the dies 3 and 4 are large, an RL converter is used, and a plurality of, for example, three, are provided at the vibration input end. By attaching the vibrator 7, the total output of the vibrator 7 can be tripled.
[0034]
Further, it is preferable that the vibration output from the vibrator 7 generates a lateral vibration or a radial vibration transmitted in the radial direction of the cavity in addition to the longitudinal vibration in the entire mold. If these complex vibrations are used, the thickness of the mold can be reduced.
The frequency generated by the vibrator 7 may be about 1 KHz to 1 MHz, but it is preferable to output an ultrasonic wave of about 10 KHz to 100 KHz in consideration of noise and the output of the vibrator.
The amplitude of the ultrasonic wave output from the vibrator 7 is determined according to the fatigue strength against ultrasonic vibration of the metal forming the fixed mold 3 or the movable mold 4. For example, the maximum amplitude when a stainless steel material is used is about 20 μm, the maximum amplitude when duralumin is about 40 μm, and the maximum amplitude when a titanium alloy is about 100 μm.
[0035]
The vibration generated by the vibrator 7 is converted in the orthogonal direction by the vibration direction converter 8 as shown in FIG. In this case, the vibration direction change body 8 and the fixed mold 3 are positioned so that the vibration resonance abdomen is located at the joint between the vibration direction change body 8 and the fixed mold 3. In addition, the cavity 6 is positioned at the abdomen of vibration resonance. In this way, the cavity 6 can be vibrated with the maximum amplitude, and the flow of the molten resin can be optimized.
[0036]
[Product release means]
In the case of injection molding of a molded product having a thin surface and fine irregularities (pits) like an optical disk, the molded product is surely released from the cavity 6 without causing pit shift or the like when the mold is opened. It is preferable to provide product release means.
In this embodiment, a protruding pin 12 as a product release means is fixed to the movable mold fixing plate 9, and its tip is inserted along the center axis X through the vibration direction changer 8 and the movable mold 4, and the cavity 6. It extends to. The protruding pin 12 is movable forward and backward by a cylinder (not shown) in order to protrude and take out the molded product formed in the cavity 6. Further, when drilling a molded product molded in the cavity 6, the protruding pin 12 is projected through the molded product by a punch mechanism 25 using the cylinder as a driving body.
[0037]
The product release means is generally the above-described protruding pin 12 that appears and disappears in the cavity 6 when the mold is opened. However, for example, other means such as a robot hand for directly taking out the molded product may be used. Good.
Alternatively, the movable mold 4 may be vibrated, or a combination of vibration of the movable mold 4 and air blow may be used. If a release means by vibration is used, it becomes unnecessary to form a taper in the unevenness of the stamper 15, the unevenness can be formed at a high density, and a disk capable of recording a large amount of information is formed. Is possible.
[0038]
【Example】
Next, experimental results performed using the ultrasonic injection mold for optical disc according to the first embodiment of the present invention will be described in comparison with a comparative example.
(1) With the fixed mold 3 and the movable mold 4 shown in FIG. Measured. as a result,
Amplitude of fixed part of movable mold (vertical / horizontal) 0.79μm / 0.35μm
Amplitude of fixed part of fixed mold (vertical direction / horizontal direction) 0.25 μm / 0.11 μm
Nozzle connection amplitude 0.42μm
Met.
[0039]
(2) As Comparative Example 1, a fixed mold and a movable mold having the same mold as those of (1) having no slit are used, and an ultrasonic wave having a frequency of 19.5 KHz is output from the vibrator by using the guide method as an inlay method. I let you. As a result of measuring the amplitude of the same part as (1),
Amplitude of fixed part of movable mold (vertical / horizontal) 1.0μm / 10μm
Amplitude of fixed part of fixed mold (vertical / horizontal) 0.35μm / 3.5μm
Nozzle connection amplitude 9.0 μm
Met.
It can be seen that the horizontal amplitude of the fixed portion and the amplitude of the nozzle connecting portion are large, and the vibration loss from the mold is extremely large. The vibrator 7 was overloaded and the oscillation stopped.
[0040]
(3) As Comparative Example 2, the same mold as (1) was used, and the guide method was used as a guide post method, and ultrasonic waves with a frequency of 19.5 KHz were output from the vibrator. As a result of measuring the amplitude of the same part as (1),
Amplitude of fixed part of movable mold (vertical direction) 1.9μm
Amplitude of fixed part of fixed mold (vertical direction) 1.7μm
Nozzle connection amplitude 3.4 μm
Met.
The amplitude of the nozzle connection portion increased by about 8 times compared to (1), and if molding was carried out as it was, there was a risk that air was entrained from the nozzle 1 to cause molding defects.
[0041]
As is clear from the above results, the amplitude of vibration transmitted in the radial direction of the cavity 6 is reduced by forming the slit 20 in the fixed mold 3 and the movable mold 4 and adopting the inlay method as the guide method. And a good molded product could be obtained.
[0042]
[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS.
FIG. 5 is a side view of a part of the ultrasonic injection mold for optical disc according to the second embodiment of the present invention, and FIG. 6 is provided with slits of the ultrasonic injection mold for optical disc in FIG. FIG.
In the second embodiment, the portion provided with the slit 20 of the fixed mold 3 and the movable mold 4 is supported by the support member 30.
[0043]
That is, when the slit 20 is formed on the back side of the region where the cavity 6 is formed as in the fixed mold 3 and the movable mold 4 of the present invention, the amplitude of radial vibration can be effectively reduced. Since the thickness of the portion becomes thin, the fixed mold 3 and the movable mold 4 are easily bent by the internal pressure of the cavity 6 at the time of injection molding. Since the bending of the molds 3 and 4 causes variations in the thickness of the molded product, in this embodiment, the portion where the slit 20 is formed by the support member 30 is supported from the back, and the mold is That is, the deflection of 3 and 4 is reduced.
[0044]
One end of the support member 30 is fixed to the fixed mold fixed plate 2 and the movable mold fixed plate 9 by bolts, welding, or the like, and the other end is fixed to the bottom 20 b of the slit 20 of the fixed mold 3 and the movable mold 4. It is in contact.
As shown in FIG. 6, a slight amount of gap is formed between the inner wall 20 a of the slit 20 and the support member 30 so that the inner wall 20 a and the support member 30 do not come into contact with each other. The width t of the gap is preferably larger than 0.1 mm so that the inner wall 20a of the slit 20 and the support member 30 do not come into contact with each other when the molds 3 and 4 are vibrated. Further, in order to keep the rigidity of the support member 30 as high as possible within a range in which the inner wall 20a of the slit 20 and the support member 30 do not contact when the molds 3 and 4 are vibrated, the width t is 0. It is preferably less than 0.5 mm, particularly less than 0.3 mm.
[0045]
Further, as the material of the support member 30, it has a Young's modulus large enough to suppress the bending of the portion where the slit 20 is formed against the pressure in the cavity 6, and the fixed mold 3 and Preferably, the movable mold 4 has a coefficient of thermal expansion substantially the same as that of the movable mold 4 (for example, the same material as that of the fixed mold 3 and the movable mold 4).
If the coefficient of thermal expansion of the support member 30 is too smaller than the fixed mold 3 and the movable mold 4, the other end of the support member 30 is separated from the bottom of the slit 20 at the time of injection molding, and the portion where the slit 20 is formed is sufficient. It becomes impossible to support. On the other hand, if the coefficient of thermal expansion is larger than that of the fixed mold 3 and the movable mold 4, the support member 30 pushes the bottom 20 b of the slit 20 with an excessive force during injection molding, and on the contrary, the fixed mold 3 and the movable mold 4. Increase the deflection.
[0046]
FIG. 7 is a plan view showing an arrangement form of the support members 30.
As shown to Fig.7 (a), although the support member 30 is good also as what is provided over the whole slit 20, if bending can be effectively suppressed in the part in which the slit 20 was formed, FIG. As shown in b), a plurality of (for example, four) slits 20 may be provided at predetermined intervals, preferably at equal intervals.
[0047]
【Example】
Hereinafter, the results of experiments conducted using the ultrasonic injection mold for optical discs according to the second embodiment of the present invention will be described in comparison with comparative examples.
(1) The second embodiment in which the support member 30 shown in FIG. 5 is provided, the guide method when the stationary mold 3 and the movable mold 4 are opened and closed is an inlay method, and an ultrasonic wave of 19 KHz is output from the vibrator. The maximum and minimum quantities were measured.
as a result
Mold internal pressure 5.5MPa
Deflection amount of mold Maximum 7μm Minimum 1μ
Met.
(2) In the same guide method as in Example 2, the maximum value and the minimum value of the deflection amount were measured in Comparative Example 3 where a support member was provided and no ultrasonic wave was output. The results are shown below.
Comparative Example 3 (with support member, without ultrasonic output):
Mold internal pressure 8.7 MPa
Deflection amount of mold Max 14μm Minimum 2μ
(3) The same guide method as in Example 2 except that the supporting member is not provided is the same as Comparative Example 1, and Comparative Example 4 is used, and the maximum value and the minimum value of the deflection amount are measured. The results are shown below.
Comparative Example 2 (no support member, no ultrasonic output):
Mold internal pressure 8.7 MPa
Deflection amount of mold Maximum 22μm Minimum 12μ
As can be seen from the above comparison results, the bending amount of the dies 3 and 4 can be greatly reduced by providing the support member 30 and further applying ultrasonic waves.
[0048]
[Third Embodiment]
A third embodiment of the present invention will be described with reference to FIG.
FIG. 8 is a cross-sectional side view of a part of an ultrasonic injection mold for optical disc according to the second embodiment of the present invention.
In this embodiment, the mounting plate 35 of the support member 30 is provided in the vicinity of the movable mold 4 so as to face the movable mold 4. The mounting plate 35 is firmly fixed to the movable mold holding member 10 with bolts or welding. The other end of the support member 30 is fixed to the mounting plate 35. As in the second embodiment, one end of the support member 20 is inserted into the slit 20 and is brought into contact with the bottom 20 b of the slit 20.
[0049]
By providing the mounting plate 35 in the vicinity of the movable mold 4, the length of the support member 30 on the movable mold 4 side can be made shorter than the support member 30 of the second embodiment. Therefore, the compressive strain in the axial direction of the support member 30 at the time of injection molding can be reduced, and the bending of the portion where the slit 20 is formed can be further reduced.
[0050]
【The invention's effect】
According to the present invention, the amplitude of vibration transmitted in the radial direction of the cavity is effectively reduced, the flow of molten resin is kept good, the transfer property is kept good, and the occurrence of birefringence and shrinkage deformation is prevented. In addition, vibration loss from the mold can be prevented as much as possible, and the mold and nozzle can be held well.
In addition, the bottom of the slit formed in the mold is supported by the support member, and the internal pressure of the mold is reduced by applying the ultrasonic wave, thereby suppressing an increase in the bending of the mold due to the decrease in the wall thickness, An optical disc having a small thickness variation can be obtained.
[Brief description of the drawings]
FIG. 1 is a side view, partially in section, showing an outline of an ultrasonic injection mold for an optical disc according to an embodiment of the present invention.
2 is a diagram for explaining a displacement waveform of vibration transmitted through the mold of FIG. 1; FIG.
FIG. 3 is a plan view of a mold showing the arrangement of slits.
FIG. 4 is a diagram showing a cross-sectional shape of a slit.
FIG. 5 is a side view showing a cross section of a part of an ultrasonic injection mold for an optical disc according to a second embodiment of the present invention.
6 is an enlarged view of a portion provided with a slit of the ultrasonic wave injection mold for optical disc of FIG. 5. FIG.
FIG. 7 is a plan view showing an arrangement form of support members.
FIG. 8 is a side view showing a cross section of a part of an ultrasonic injection mold for an optical disc according to a third embodiment of the present invention.
[Explanation of symbols]
1 nozzle
2 Fixed mold fixing plate
3 Fixed mold
4 Movable mold
5 Sprue
6 cavity
7 vibrator
8 Vibration direction change body
9 Movable mold fixed plate
10 Movable mold holding member
11 Hydraulic cylinder
12 Protruding pin (product release means)
15 Stamper
17 Convex
20 slits
20a Inner wall of slit
30 Support member
35 Mounting plate (Mounting member)

Claims (13)

A movable mold and a fixed mold, a disk molding cavity formed on the contact surface of the movable mold and the fixed mold, and an unevenness formed on the surface of the disk disposed at the bottom of the cavity. An ultrasonic injection mold for an optical disc comprising a stamper and an ultrasonic wave generating means attached to the movable mold or the fixed mold for applying ultrasonic waves to the cavity during injection molding,
Forming one or a plurality of slits in the direction intersecting the radial direction of the cavity on the back side of the region where the cavity of the movable mold and the stationary mold is formed;
Ultrasonic injection mold for optical disks characterized by When the wavelength of the ultrasonic wave transmitted in the radial direction of the cavity is λ,
2. The slit is formed at nλ / 4 (n = 1, 3, 5,...) From an ultrasonic wave input portion for inputting the ultrasonic wave to the movable mold or the fixed mold. An ultrasonic injection mold for optical discs as described in 1. 3. The ultrasonic injection mold for an optical disk according to claim 1, wherein the slits are formed in a plurality of rows from the outer peripheral edge of the cavity toward the inside. The said ultrasonic wave generation means is provided in the input end of the vibration direction change body by which the output end was connected with the said ultrasonic input part of the said movable metal mold | die or the said fixed metal mold | die. The ultrasonic injection mold for optical discs according to any one of the above. Product release means for releasing the injection-molded product from the cavity is provided in either the vibration direction changer to which the movable mold and the ultrasonic wave generation means are attached or the fixed mold. The ultrasonic injection mold for optical discs according to any one of claims 1 to 4. 6. The optical disk according to claim 5, wherein the product releasing means releases the product from the cavity by vibrating the movable mold or the fixed mold having the stamper. Sonic injection mold. The vibration direction changing body to which the movable mold and the ultrasonic wave generation means are attached or the fixed mold is provided with punch means for punching a predetermined part of an injection molded product. The ultrasonic injection mold for optical discs according to any one of 1 to 6. The ultrasonic injection molding for optical disks according to any one of claims 1 to 7, wherein guides of the movable mold and the fixed mold at the time of mold clamping or mold opening are performed by inlay-type guide means. Mold. 2. The ultrasonic wave generating means generates transverse vibrations or radial vibrations transmitted in a radial direction of the cavity in addition to longitudinal vibrations on the whole of the fixed mold and the movable mold. The ultrasonic injection mold for optical disks according to any one of -8. The ultrasonic injection mold for optical discs according to any one of claims 1 to 9, wherein a support member is inserted into the slit, and a bottom portion of the slit is supported at one end of the support member during injection molding. . 11. The ultrasonic injection mold for optical disc according to claim 10, wherein a width t of a gap between the support member and the inner wall of the slit is in a range of 0.1 mm <t <0.3 mm. Type. The other end of the support member is attached to a fixed mold fixing member that fixes the fixed mold or a movable mold fixing member that fixes the movable mold. Ultrasonic injection mold for optical discs. The ultrasonic injection mold for optical disks according to claim 10 or 11, wherein an attachment member is provided in the vicinity of the fixed mold or the movable mold, and the support member is attached to the attachment member.

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