JPH065142Y2 - Injection mold for optical disk molding - Google Patents

Description

TECHNICAL FIELD The present invention relates to improvement of an injection molding die for molding an optical disc, and more specifically, a stamper for transferring recorded information to an optical disc is provided on a cavity wall surface of the injection molding die. Regarding the improvement of the stamper holder to be fixed.

(Prior Art) Conventionally, as shown in FIG. 4, recording on an optical disk is performed in a cavity 3 constituted by a fixed mold 1 and a movable mold 2 as a pair of molds facing each other. An injection molding die for molding an optical disc, which is provided with a stamper 4 for transferring information, is known. With this conventional injection mold,
Stamper retainer 5 for fixing stamper 4 to die 2
Are attached by bolts 6. The stamper retainer 5 has a ring plate shape as shown in FIG.

This stamper retainer 5 has a function of pressing the stamper 4 to the mold 2 while pressing the stamper 4 toward the cavity wall surface 8 of the mold 2 from the thickness direction while circulating the outer peripheral portion 7 of the stamper 4 in the circumferential direction. . The stamper retainer 5 cooperates with the mold 1 and the mold 2 to form the cavity 3,
Clamping pressure is applied to the stamper retainer 5 by the cavity wall surface 9 of the mold 1 when the mold 1 and the mold 2 are clamped. The injection molding of an optical disk is performed by clamping the mold 1 and the mold 2 and then filling the molten resin 10 with the stamper holder 5 so as to release gas at the side facing the cavity wall surface 9 at the time of filling. The gas vent passage 11 is formed as shown in FIG.

By the way, when the optical disk is injection-molded by being filled with the molten resin 10, the central portion 13 of the stamper 4 that is not in surface contact with the pressing portion 12 that presses the stamper 4 against the cavity wall surface 8 by the resin pressure during the injection molding. Is compressed, the thickness of the central portion 13 becomes thin, and there is a phenomenon in which the central portion 13 tries to expand toward the outer peripheral portion 7 by that amount. However, in this conventional injection molding die, the surface of the stamper holder 5 facing the cavity wall surface 9 contacts the cavity wall surface 9 over the entire circumference in the circumferential direction, and the stamper holder 5 is removed except for the gas vent passage 11. Since the mold clamping pressure of the mold 1 is applied to the whole, the stamper 4 is uniform when the stamper 4 tries to extend from the central portion 13 toward the outer peripheral portion 7 (direction of arrow A shown in FIG. 4). However, the stamper 4 is distorted in the vicinity of the boundary between the central portion 13 and the outer peripheral portion 7 due to the resin pressure of the molten resin 10 at the time of injection molding, and the transferability to the optical disc deteriorates. However, there is a problem that the optical characteristics of the optical disc deteriorate, such as a birefringence phenomenon, and the molding quality of the optical disc deteriorates.

(Purpose of Invention) The present invention has been made in consideration of the above circumstances, and an object thereof is to prevent distortion at the time of injection molding of an optical disk based on a stamper holder, and thus to improve the molding quality of the optical disk. The present invention is to provide an injection molding die for molding an optical disk.

(Structure) The present invention provides a stamper retainer that circulates the outer peripheral portion of a stamper for transferring recorded information to an optical disc in the circumferential direction and presses against the cavity wall surface of one of the pair of molds from the thickness direction thereof. The mold is attached to the one mold so as to form a cavity in cooperation with the pair of molds, the mold and the stamper retainer are subjected to mold clamping pressure, and the molten resin is filled into the cavity to eject an optical disc. In an injection-molding die for molding an optical disk, a pressing portion of the stamper holder that presses the stamper against a cavity wall surface of the one die has a cavity wall surface of the other die as the molten resin is filled. A gap extending in the circumferential direction between the cavity wall surface of the other mold and the pressing portion is formed over the entire circumference so that the stamper pressing A portion other than the pressure portion is in contact with both cavity wall surfaces of the pair of molds to serve as a mold clamping pressure receiving portion, and a gas vent passage is formed in the mold clamping pressure receiver portion. Is communicated with the gap.

An embodiment of an injection molding die for molding an optical disk according to the present invention will be described below with reference to the drawings.

In FIG. 1, 20 is an injection molding die for molding an optical disk. The injection molding die 20 has die mounting plates 21 and 22 facing each other. The guide rods 23 and 24 are fixed to the mold mounting plate 21, and the mold mounting plate 22 is the guide rod 2
It is reciprocated along 3 and 24. A movable mold 25 is fixed to the mold mounting plate 22, a fixed mold 26 is fixed to the mold mounting plate 21, and the molds 25 and 26 are a pair of molds facing each other. Are configured.

FIG. 1 shows the mold clamping state of the molds 25 and 26.
27 indicates a cavity, in which the nozzle is
The molten resin 30 is supplied through the spool 28 and the spool 29, 31 is a nozzle touch, and 32 is a gate. A stamper 33 is arranged in the cavity 27, and a pit for transferring recorded information to the optical disc is formed in the stamper 33. The stamper 33 has a thickness of approximately 0.3 mm, and its shape is a donut plate type. This stamper 33
Is fixed to one of the molds 25 by a stamper retainer 34, and this stamper retainer 34 has a ring plate shape as shown in FIG.

The stamper retainer 34 circulates the outer peripheral portion 35 of the stamper 33 in the circumferential direction and presses it from the thickness direction toward the cavity wall surface 36 of the mold 25 of one mold as shown in an enlarged view in FIG. A fixing portion 38 that has a bolt 37 and is fixed to the mold 25 by a bolt 37, and a pressing portion 39 that presses the outer peripheral portion 35 of the stamper 33.
It consists of and. The fixing part 38 functions as a mold clamping pressure receiving part that is in contact with both cavity wall surfaces of the pair of molds and receives the mold clamping pressure. The pressing portion 39 is configured to be able to bend toward the cavity wall surface 40 of the other mold 26, and a gap 41 extending in the circumferential direction is provided over the entire circumference between the cavity wall surface 40 and the pressing portion 39. Has been formed.
The gap 41 is approximately 0.02 mm to 0.05 mm. This gap 41
Is formed by providing a circular step portion 41 ′ on the inner peripheral side of the stamper holder 34.

The fixed portion 38 has a gas vent groove 42 extending in the radial direction on the side facing the cavity wall surface 40 (parting surface).
However, the stamper holder 34 is formed with an appropriate interval in the circumferential direction of the stamper holder 34, and the gap 41 communicates with the gas vent groove 42 and constitutes a gas vent passage when the molten resin is filled. The pressing portion 39 receives the mold clamping pressure by the fixing portion 38 that comes into contact with the cavity wall surface 40 of the other mold 26 at the time of mold clamping, and as shown in FIG.
The central portion of the stamper 33 that is not in surface contact with the pressing portion 39
When the thickness of 50 is reduced and the stamper 33 extends from the central portion 50 toward the outer peripheral portion 35 and the wall thickness of the outer peripheral portion 35 is about to increase, the stamper 33 bends in the direction of arrow B.

As a result, the stamper 33 smoothly extends from the central portion 42 toward the outer peripheral portion 35 as the molten resin is filled,
An optical disc is injection-molded without distortion.

(Effects of the Invention) As described above, the injection mold for optical disk molding according to the present invention extends from the thickness direction while going around the outer peripheral portion of the stamper for transferring the recording information to the optical disk in the circumferential direction. Of the stamper holders that press against the cavity wall surface of one of the pair of molds, the pressing portion that presses the stamper against the cavity wall surface of one mold is the cavity wall surface of the other mold as the molten resin is filled. A cavity extending in the circumferential direction is formed over the entire circumference between the cavity wall surface of the other mold and its pressing portion so that it can be bent toward. Since it is a mold clamping pressure receiving part that receives mold clamping pressure in contact with both cavity wall surfaces of the mold, and a gas vent passage is formed in this mold clamping pressure receiver, and this gas vent passage is communicated with the gap,
It is possible to prevent distortion at the time of injection molding of the optical disk based on the stamper pressing without impairing the mold clamping pressure, and since the gap is connected to the degassing passage, the gas can be smoothly discharged. The effect that the improvement of molding quality can be expected is achieved.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing the entire structure of an injection molding die for optical disk molding according to the present invention, FIG. 2 is an enlarged plan view showing the shape of the stamper holder shown in FIG. 1, and FIG. FIG. 4 is a partial cross-sectional view showing an enlarged main part of the injection mold shown in FIG. 1, FIG. 4 is a partial cross-sectional view showing the main part of a conventional injection mold for optical disk molding, and FIG. It is a top view of the stamper presser shown in the figure. 20 ... Injection mold 25, 26 ... Mold 30 ... Molten resin 33 ... Stamper 34 ... Stamper retainer 35 ... Perimeter 36 ... Cavity wall 40 ... Cavity wall 41 ... Gap

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G11B 7/24 Z 7215-5D // B29L 17:00 4F

Claims (1)

[Scope of utility model registration request] 1. A pair of stamper retainers that presses against a cavity wall surface of one of a pair of molds from the thickness direction while circling around the outer peripheral portion of the stamper for transferring recorded information to an optical disk. The mold is attached to the one mold so as to form a cavity in cooperation with the mold, and the mold and the stamper retainer are subjected to mold clamping pressure to fill the cavity with molten resin and injection-mold an optical disk. In an injection-molding die for optical disk molding, a pressing portion of the stamper retainer that presses the stamper against the cavity wall surface of the one die faces the cavity wall surface of the other die along with the filling of the molten resin. In order to be able to bend due to bending, a gap extending in the circumferential direction is formed over the entire circumference between the cavity wall surface of the other mold and the pressing portion. An outer portion is in contact with both cavity wall surfaces of the pair of molds to form a mold clamping pressure receiving portion for receiving a mold clamping pressure, and a gas vent passage is formed in the mold clamping pressure receiver, and the gas vent passage is defined by An injection mold for optical disk molding, characterized by being communicated with a gap.