JP2002347093A - Mold for injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold apparatus for injection molding which molds in a high cycle, which improves transferability of high density pits, and which prevents a thermal influence of a protruding part in a mold for injection molding a thin plate-like molding such as a CD or the like. SOLUTION: The mold for injection molding comprises a fixed side mold 2 having a first end plate 23 at one surface side, and a movable side mold 4 having a second end plate 43 so as to form a cavity 8 oppositely to the first end plate side of the fixed side mold. At least at one of the first and second end plates, mold plates 22 and 42 having cooling means 27 and 47 provided at opposite surfaces to cavity forming surfaces to cool the plates 23 and 43 are coupled, mounting plates 21 and 42 are coupled at opposite surfaces of the plates 22 and 42 to the end plates 23 and 43, and heat insulation grooves 6 and 7 are respectively provided at coupling surfaces 21a and 41a of the plates 21 and 41 to the plates 22 and 42.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a compact disc (CD), a digital versatile disc (DV), for example.
D), fine irregularities (called pits) such as optical discs such as mini discs (MD) and light guide plates of liquid crystal display devices.
When forming a thin plate-like body on which a micron-sized unevenness for recording and reproducing information by laser light formed on a CD is formed by injection molding, the molten resin injected into the cavity is made uniform. The present invention relates to an injection mold capable of transferring unevenness precisely and hardening in a short time.
More specifically, the present invention relates to an injection mold capable of keeping the temperature of a mirror plate of a mold forming a thin-plate cavity at a temperature suitable for molding.

2. Description of the Related Art For example, a compact disk (hereinafter referred to as a CD)
) Is formed in a structure as shown in FIG. That is, the fixed mold 2 and the movable mold 4 are formed, and a cavity (cavity) 8 for forming a compact such as a CD is formed between the fixed mold 2 and the movable mold 4. The fixed mold 2 includes a mounting plate 21, a mold plate 22, a fixed mirror plate 23, and a mirror plate mounting plate 24 for fixing the fixed mirror plate 23, and the sprue portion 3 penetrates a central portion thereof. I have. The sprue portion 3 is formed with a sprue bush 31 in which a through hole 32 is formed so that the molten resin flows into the cavity 8 at the center. This fixed mirror plate 2
Water channels 25 and 26 are connected to the back surface of 3 so that cooling water (warming water) can flow, and cooling water (or hot water) flows from an external supply device (not shown) to maintain the mirror plate 23 at a constant temperature. The mold plate 22 having the cooling means 27 is fixed in such a manner. Similarly, the movable mold 4 also includes a mounting plate 41, a mold plate 42, a movable mirror plate 43, and a movable mirror plate mounting plate 44.
And a protruding portion 5 is formed penetrating through the central portion thereof. The protruding portion 5 has a centrally located protruding pin 51 for protruding a resin (sprue) portion solidified in the through hole 32 of the sprue portion 3, and a CD formed in the cavity 8 on the outer periphery of the protruding pin 51. A punch-type core 52 for punching out a central portion of the mold with a sprue, and a protruding bush 53 for projecting a molded body such as a CD whose central portion has been punched out from the cavity 8. Water passages 45 and 46 are connected to a surface of the movable side mirror plate 43 on the side opposite to the cavity so that cooling water (warming water) can flow, similarly to the fixed side mirror plate 23, and an external supply device (not shown) The mold plate 42 having the cooling means 47 is fixed so that cooling water (or warm water) flows from the substrate and the mirror plate 43 is maintained at a constant temperature. Further, since the protruding portion 5 is present at a substantially central portion of the mounting plate 41, when this portion is heated to a high temperature by the temperature of the molten resin, the mechanisms are distorted, and a punching failure by the punch core 52 occurs. Also, due to the temperature rise of the projecting pin 51 or the projecting bush 53, the projecting portion is softened at the time of projecting, and a projecting failure occurs. Therefore, the cooling water passage 4 is provided inside the mounting plate.
8 and 49 for cooling the mounting plate and the protrusion 5. Further, in the injection molding die for molding a DVD, since the unevenness of the pits of the DVD is formed at a high density, the molten resin is injected from the spool portion 3 into the cavity 8 and immediately before the solidification is started, the compression mechanism (FIG. (Not shown), the movable high-density pits are transferred by slightly moving the movable-side mirror plate 43 in the fixed side direction and compressing the molten resin immediately before solidification. That is, in order to accurately transfer DVD pits, the molten resin is compressed as described above.
It is known that if the molding temperature is maintained at a temperature immediately before solidification of the molten resin during the compression, transferability is good. Therefore, until the compression is completed, the temperatures of the cooling means 47, 48, and 49 provided on the template 42 and the mounting plate 41 are finely adjusted so that the temperature of the mirror plate 43 is not excessively lowered.
In order to prevent the temperature from becoming high, cooling water (or hot water) is supplied from an external temperature control device (not shown) to finely control the temperature. Using the above injection mold,
A resin melted at about 300 to 360 ° C. from the center of the sprue part 3 is poured into the cavity 8 (in the case of a DVD, the movable-side mold is pressed by a pressurizing device (not shown) immediately before solidification starts). The pits are transferred.) At the time when the cooling unit starts to cool and substantially harden, the center part is punched by the punch-shaped core 52 of the protruding part 5, and the punched center part is further separated by the protruding pin 51. By taking out a CD, which is a molded body whose central portion is punched out by the protruding bush 53, from the cavity 8,
A molded article is obtained.

Injection molding dies generally have the above-mentioned structure. However, in recent years, CDs have become very cheap, and the molding speed has been increased (C
Due to the molding time per D sheet of 5 to 6 seconds), high cycle molding has been realized to reduce the processing cost. Therefore, when the injection of the molten resin (in the case of DVD, a compression step is added) is completed, it must be rapidly cooled.
In particular, in a DVD, the track pitch is about 0.7.
It is a very high density pit with a minimum pit length of about 0.4 μm and the minimum pit length must be maintained at the temperature just before solidification of the molten resin until compression is completed in order to transfer the high density pit. Must. Also, the temperature of the mirror plate must be conducted to the mounting plate through the mold plate due to the temperature of the molten resin (300 to 360 ° C.), and the temperature of the mounting plate does not adversely affect the operation of the projecting portion due to an increase in the temperature of the mounting plate. No. The present invention has been made in order to solve such a problem, and it is an object of the present invention to provide an injection molding die that realizes high cycle molding, improved transferability of high-density pits, and prevention of thermal effects of protrusions. Aim.

SUMMARY OF THE INVENTION An injection molding die according to the present invention has a fixed die having a first mirror plate on one surface side and a cavity opposed to the first mirror plate side of the fixed die. And a movable mold having a second mirror surface plate.
At least one of the second mirror plate and a mold plate provided with cooling means for cooling the mirror plate is coupled to a surface opposite to the cavity forming surface, and the template is held on a surface of the template opposite to the mirror plate. And the mounting plate has a heat-insulating groove on the connecting surface between the template and the mounting plate. Further, the heat insulating groove is formed by a cavity. In the heat insulating groove, the cavity may be filled with a heat insulating material.

Next, an injection mold according to the present invention will be described with reference to the drawings. As shown in FIG. 1, the injection mold according to the present invention has a fixed mold 2 having a first mirror plate 23 on one surface side and a first mold 2 of the fixed mold 2, as shown in a sectional explanatory view of the waist portion. The movable mold 4 has a second mirror plate 43 so as to form the cavity 8 facing the mirror plate 23 side. The fixed mold 2 is
As shown in FIG. 1, the sprue unit 3 includes a mounting plate 21, a template 22, a mirror plate 23, and a mirror plate mounting plate 24 for fixing the mirror plate 23. The sprue part 3 has a cavity 8
The sprue bush 31 is formed with a through hole 32 formed so as to flow through. Water passages 25 and 26 are connected to the surface of the fixed-side mirror plate 23 on the side opposite to the cavity 8 so that cooling water (warming water) can flow, and cooling water (or hot water) is supplied from an external supply device (not shown). Shed, mirror plate 2
The template 22 having cooling means 27 for cooling the mold 3 is fixed. A mounting plate 21 having a spool bush 31 at the center is fixed to the opposite side of the mirror plate 23 of the template 22. Also, as shown in FIG.
A heat insulating groove 6 is formed in the coupling surface 21a fixed to the first surface. The heat insulating groove 6 may be provided on either the template 22 or the mounting plate 21, and is provided on the mounting plate 21 in this embodiment. Further, the heat insulating groove 6 is a concave depression formed in the mounting plate 21 and may be hollow inside, or the inside of the groove may be filled with a heat insulating material such as asbestos. In this embodiment,
Since the cavity 8 is formed in a disc shape such as a CD, the cavity 8 is arranged concentrically in accordance with the shape. However, the cavity 8 may be arranged in an effective shape according to the cavity shape. Similarly, the movable mold 4 also includes a mounting plate 41, a mold plate 42, a mirror surface plate 43, and a mirror surface mounting plate 44, and a protruding portion 5 is formed through a central portion thereof. The protruding portion 5 has a centrally located protruding pin 51 for protruding a resin (sprue) portion solidified in the through hole 32 of the sprue portion 3, and a CD or the like formed in the cavity 8 on the outer periphery of the protruding pin 51. A punch-type core 52 punches out a central portion with a sprue, and a projecting bush 53 that projects a molded body such as a CD whose central portion is punched out from the cavity 8. The cooling means 47 is formed on the surface of the mirror plate 43 on the side opposite to the cavity 8, similarly to the fixed mirror plate 23.
A mold plate 42 having cooling means 47 for cooling the mirror surface plate 43 by flowing cooling water (or warm water) by 5 and 46 is fixed. A mounting plate 41 having a protruding portion 5 at the center is fixed to the opposite side of the mirror plate 43 of the template 42. Also, as shown in FIG.
A heat insulating groove 7 is formed in the coupling surface 41a fixed to the first surface. The heat insulating groove 7 may be provided on either the template 42 or the mounting plate 41, and is provided on the mounting plate 41 in this embodiment. Further, the heat insulating groove 7 is a concave depression formed in the mounting plate 41 and may be hollow inside, or the inside of the groove may be filled with a heat insulating material such as asbestos. Further, similarly to the heat-insulating groove 6 on the fixed side, the heat-insulating groove 7 is not limited to the concentric shape but may be arranged in an effective shape according to the cavity shape. The mounting plate 41 is fixed to a clamping plate 11 of the injection molding machine, as shown in a plan view of the injection molding machine in FIG. And the molten resin heated by the heating / injection device 14 and melted into the mud is sent to the sprue unit 3 side. Similarly, in the movable mold 4, the mounting plate 41 is fixed to the clamping plate 12 of the injection molding machine as shown in FIG. In FIG. 4, reference numeral 15 denotes a mold clamping device. The injection molding die is closed by a mold clamping device, and molten resin is injected into the cavity 8 from the gate of the heating injection device 14. However, in an injection molding machine for molding a DVD having high-density pits, after the mold is clamped by the mold clamping device, the mirror plate 43 is slightly advanced to a fixed side by a compression device (not shown) to fill the cavity. The compressed molten resin is compressed, and pits engraved on the mirror surface are transferred. Although not shown, the mirror plates 23, 4 of the fixed mold 2 or the movable mold 4 are not shown.
A stamper having fine irregularities corresponding to the pits or grooves formed on the CD is attached to one of the three, and a row of fine pits (irregularities) is formed on one surface of the CD along the circumferential direction. Next, using this injection molding machine,
A method for forming a CD will be described. First, when the above-mentioned fixed mold 2 and movable mold 4 are pressed into contact with each other and a resin made of, for example, polycarbonate and melted at about 300 to 360 ° C. is injected, the resin enters the cavity through the through hole in the sprue bush 31. Is filled. Particularly, in the case of a thin plate-like molded product having high-density pits such as a DVD, just before the molten resin is filled and the resin is solidified, the molten resin that has been solidified is pressed by a compression mechanism (not shown) to produce a mirror surface portion. The irregularities of the pits engraved on the substrate are completely transferred to the resin. During this time, warm water of about 70 to 130 ° C. is supplied to the cooling means.
Since transfer cannot be performed if the solidification is complete, the semi-molten state immediately before solidification is ideally suited for transfer. ) Is managed. When the transfer is completed and the resin cools and solidifies, a CD shaped by the cavity 8 is formed. Next, the central portion (gate portion) of the CD is punched out by moving the punch core 52 toward the fixed mold 2 side. Then, the movable mold 4
Is separated from the fixed mold 2 so that the cured portion of the resin is separated from the fixed mold together with the movable mold. Thereafter, by further projecting the projecting pin 51, the sprue portion is completely separated from the CD, and further, by pushing up the projecting bush 54, the CD is separated and taken out from the movable mold. Thereafter, by repeatedly pressing the movable mold against the fixed mold and filling the cavity with the molten resin, CDs can be similarly manufactured one after another. The CD is formed into a product by forming a reflective film such as a metal on a surface on which fine irregularities are formed, and further forming a protective film on the surface. According to the injection molding mold of the present invention, by providing a blocking groove between a mold plate having a cooling means for cooling the mirror plate and the mounting plate, heat of the mirror plate and the mold plate is insulated, Until the transfer of high-density pits and grooves is completed by the compression device for injection molding dies such as DVDs, the temperature of the mirror plate is maintained at the transfer temperature immediately before the molten resin solidifies, and the best transferability is maintained. As a result, a high quality DVD can be obtained. Also, since heat from the template to the mounting plate is insulated,
The cooling effect by the cooling means of the template effectively acts on the mirror plate. As a result, while satisfying various characteristics as a disk, the cycle from injection of the molten resin to curing and removal from the mold is shortened, and even in high cycle molding where the number of cycles per unit time is increased, It is possible to obtain a thin plate-like molded product such as a CD that satisfies various characteristics as described above. In addition, since the space between the mold plate and the mounting plate is insulated by the heat-insulating groove, the temperature of the mirror plate and the mold plate alone stays at a change in temperature. Even if it rises, it can be cooled quickly in a short time, the molded product is solidified from the injection of the molten resin into the cavity, and the cycle from the next injection to the next injection can be shortened. That is, as shown in FIG. *, The temperature distribution of the mold during the high cycle molding shows that the mold plate is not deformed even if the cavity surface of the mirror surface portion rises to 300 to 350 ° C. (temperature a shown in the graph of FIG. 5). 70 near the mounting plate
The temperature is kept at about 110 ° C. (temperature b shown in the graph of FIG. 5), and the temperature of the mounting plate is kept at 100 ° C. or less. Therefore, a rise in the temperature of the mounting plate 41 can be prevented, and a temperature distortion of the protruding pin 51 of the protruding portion 5, the punch core 52, the protruding bush 53, and the like can be prevented.
Poor punching of the gate by the punch-type core 52 and poor protrusion due to softening of the protruding portion due to a rise in temperature of the protruding pin 51 or the protruding bush 53 can be prevented. In addition, the heat insulating groove eliminates the need to extend a cooling water passage inside the mounting plate as in the conventional case, thereby achieving an effect of cost reduction. In the present embodiment, the heat insulating groove is formed on both the first mirror plate of the fixed mold and the second mirror plate of the movable mold. Can be configured to use a conventional cooling method. Also, in the example of manufacturing a CD or DVD,
This is particularly effective when manufacturing thin-formed products such as optical discs such as MDs and light guide plates for liquid crystal display devices in a short time. However, injection molding is used to mold large-sized products even if they are not thin products. The use of the heat-insulating groove of the present invention in a mold is effective in increasing the molding cycle and preventing the temperature of the ejector mechanism from rising.

According to the heat-insulating groove of the present invention, the temperature of the mirror plate is kept at the transfer temperature immediately before the molten resin is solidified until the transfer of the pits and grooves is completed in the injection mold having the compression device. It is possible to obtain the best quality DVD while maintaining the best transferability. In addition, the heat insulating groove allows the temperature to remain at the volume of only the mirror plate and the template plate, allows rapid cooling in a short time, and enables high cycle molding. Therefore, processing costs for CDs and the like can be reduced. In addition, the heat-insulating groove can prevent the temperature distortion of the protruding portion, and can prevent the punching defect due to the punch-type core and the protruding defect due to the softening of the protruding portion due to the rise in the temperature of the protruding pin or the protruding bush. A good CD or the like can be formed. In addition, the heat insulating groove eliminates the need to extend the cooling water passage inside the mounting plate as in the conventional case, thereby achieving an effect of cost reduction.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of a mold according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line XX of FIG.

FIG. 3 is a sectional view of the heat insulating groove 7 of the mounting plate 41 taken along the line YY.

FIG. 4 is an explanatory diagram showing the overall configuration of the injection molding machine.

FIG. 5 is a graph showing a temperature distribution of each part at the time of molding a CD using an injection mold according to the present invention.

FIG. 6 is an explanatory sectional view showing a main part of an injection molding machine for molding a conventional CD.

[Explanation of symbols]

 23 First mirror surface plate 2 Fixed mold 43 Second mirror plate 4 Movable mold 8 Cavity 27,47 Cooling means 22,42 Mold plate 21,41 Mounting plate 21a, 41a Coupling surface 6,7 Thermal insulation groove

Claims (3)

[Claims] 1. A fixed mold having a first mirror plate on one surface side, and a movable mold having a second mirror plate so as to form a cavity facing the first mirror plate side of the fixed mold. A mold having at least one of the first and second mirror-faced plates coupled to a surface opposite to the cavity forming surface and provided with cooling means for cooling the mirror-faced plate; An injection mold having an attachment plate for holding the template attached to a surface opposite to the mirror surface plate, and having a heat-insulating groove on a joint surface between the template and the attachment plate. 2. The injection mold according to claim 1, wherein said heat-insulating groove is formed as a cavity. 3. The injection molding die according to claim 2, wherein said heat insulating groove is formed by filling a cavity with a heat insulating material.