JP2514868B2 - Injection mold for molding information recording board - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold used for injection molding of an information recording board such as an optical disk.

[0002]

2. Description of the Related Art This type of injection mold includes a movable mold having a punch whose axial end surface is located at the center of a cavity and which is movable in the axial direction, and a fixed mold having a sprue provided on the opposite mold surface of the punch. The mold surface of the cavity is mirror-finished including the facing mold surface.

Injection molding of an information recording disk is carried out by injecting and filling resin into the cavity from the sprue, and before the resin is completely solidified, the center portion of the molded product formed by the punch is used for the purpose of gate cutting. We are punching.

[0004]

The problem with the conventional injection mold described above is that when the cooling time is shortened in order to achieve a high molding cycle, the tip of the eject pin inside the punch is formed into an undercut. Also, the center part of the molded product punched out before the mold opening remains attached to the facing mold surface of the punch of the fixed mold when the mold is opened, and it becomes difficult to remove the sprue and runner by the eject pin. .

The cooling time of the mold in this case is the time from the completion of injection to the start of mold opening, and the surface roughness of the cavity surface including the facing mold surface of the punch is Rmax: 0.
In the conventional injection mold having a size of 02 μ, when the cooling time is shortened, the punched central part of the molded product tends to remain on the fixed mold side when the mold is opened from around 2.5 seconds.

For this reason, in the conventional mold, there is a limit to shortening the cooling time to make the molding cycle high cycle, and in order to perform the high cycle molding by further shortening the cooling time, the molded product is It is necessary to have a means for preventing the punched central part from remaining.

The present invention is intended to solve the above-mentioned conventional problems, and an object thereof is to treat the surface of the facing mold surface of the punch with a rougher surface than the mold surface for molding the molded article. It is possible to prevent the punched center part from remaining on the fixed mold side.
Accordingly, it is to provide a new mold for injection molding of an information recording board that enables a high molding cycle by shortening the cooling time.

[0008]

SUMMARY OF THE INVENTION According to the present invention according to the above object, there is provided a movable die having a punch whose axially end surface is located in the center of a cavity and which is movable in the axial direction, and a sprue which is provided on an opposing die surface of the punch. In an injection mold for molding an information recording board, which comprises a mold, a surface roughness capable of preventing escape of air from the mold face, which occurs during injection filling of the opposite mold face, is 10 μ.
It is formed on a rough surface of ˜100 μ.

[0009]

In the above injection mold, since the facing surface of the punch is formed to have a surface roughness of 10 μ to 100 μ,
The escape of air from the mold surface during injection filling is blocked by the rough surface on the opposed mold surface, and air remains between the opposed mold surface and the soft resin.

Even if the resin is compressed by the tip surface of the punch, this residual air is not easily removed by the pressure at that time. The central portion of the molded product that has been pulled out is in close contact with the front end surface of the punch and is easily separated from the opposing mold surface, and does not remain on the fixed mold side even when the mold is opened.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the figure, 1 is a movable mold, 2 is a fixed mold, and a cavity 3 for molding an information recording disk is formed on the parting surfaces of both molds.

A cylindrical punch 5 housed in a sleeve 4 is provided at the center of the movable die 1 so as to be movable in the axial direction. The tip end of the punch 5 is located at the center of the cavity 3 by forming the tip end surface in a concave shape, and an eject pin 6 whose tip is undercut is inserted in the inside so as to be able to move forward and backward.

The fixed mold 2 is provided with a sprue bush 7 having the same diameter as the punch 5 at a position opposed to the punch 5, and a cylindrical guide member 8 and an inner peripheral ring 9 are concentric circles around the sprue bush 7. It is provided in.

The inner end surface of the sprue bush 7 is located in the mold as the facing mold surface 10 of the punch 5, and the sprue 11 is open at the center of the facing mold surface 10. Further, an annular gate is formed between the peripheral edge of the sprue bush 7 and the peripheral edge 5a of the punch tip protruding into the mold, whereby a runner 12 is provided between the punch tip surface and the opposing mold surface 10. ing.

The mold surface excluding the runner portion of the cavity 3 is mirror-finished to have a surface roughness Rmax: 0.02 μ, but the opposing mold surface 10 of the punch 5 in the runner portion has a surface roughness of 10 μ to 100 μ. Is formed on the rough surface of. The surface treatment of the facing mold surface 10 can be performed by embossing, electric discharge machining, sandblasting, or the like. Reference numeral 13 is a stamper, and 14 is a stamper holder provided on the fixed mold side.

In the above injection mold, the molten resin injected and filled from the sprue 11 into the runner 12 flows into the cavity 3 from the annular gate, and is formed into a disk-shaped molded product on which information is recorded.

After injection filling, the punch 5 is moved forward to punch the center of the molded product from the annular gate portion before the molded product is completely solidified for the purpose of removing the sprue and runner of the molded product. . The resin filled between the punch tip surface and the facing mold surface 10 by this punching is strongly pressed until the punching is completed.

In this case, if the facing mold surface 10 is mirror-finished with high precision as in the conventional case, the central portion of the molded product is brought into close contact with the facing mold surface 10 when the cooling time is 2.5 seconds or less. This tendency becomes remarkable as the cooling time is further shortened.

When the die is opened under such a state, even if the tip of the eject pin 6 is formed undercut, the central portion of the eject pin 6 is in close contact with the facing die surface 10 of the punch 5 and is placed on the fixed die side. The remainder cannot be removed from the cavity 3 by the eject pin 6.

However, on the opposed mold surface 10 formed with a rough surface having a surface roughness of 10 μ to 100 μ, escape of air from the mold surface which occurs during injection filling is blocked by the rough surface, and the resin of the runner 12 is prevented. Air will remain between the and the opposite mold surface 10. Since this residual air is difficult to be removed by pressing with the punch 5, the adhesion of the resin to the facing mold surface 10 is extremely smaller than that of the mirror finish, and the punched part of the molded product adheres to the tip of the punch as the mold opens and faces it. Mold surface 1
Move away from zero.

In particular, when the surface roughness is set to Rmax: 10 μ, even if the cooling time is shortened to 1.5 seconds, there is no adhesion to the fixed mold side, and the punched out portion by the eject pin 6 is surely eliminated. It can be carried out.

As described above, according to the present invention, the surface roughness of the opposing mold surface 10 of the punch 5 of the injection mold for molding the information recording board is such that the escape of air from the mold surface caused during injection filling can be prevented. Is formed on a rough surface of 10 μ to 100 μ, and even if the cooling time is shortened, the punched portion of the molded product by the punch 5 is prevented from adhering to the fixed mold side. Therefore, the cooling time is shortened. The molding cycle can be made high cycle.

Further, since it suffices to roughen the facing die surface of the punch by a commonly used means, the die structure does not become particularly complicated, and the conventional injection molding for information recording disk molding is performed. Since it can be carried out without changing the structure of the mold, the cost will not increase.

[Brief description of drawings]

FIG. 1 is a sectional view of an injection mold for molding an information recording board according to the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part.

FIG. 3 is an enlarged front view of a main part.

[Explanation of symbols]

 1 Movable Type 2 Fixed Type 3 Cavity 5 Punch 5a Peripheral Blade 6 Eject Pin 7 Sprue Bushing 10 Opposing Surface 11 Sprue 12 Runner

Claims (1)

(57) [Claims] 1. An information recording disk molding injection comprising a movable mold having a punch whose axially end surface is located in the center of a cavity and which is movable in the axial direction, and a fixed mold provided with a sprue on the surface of the punch facing the punch. In the mold, 10 μ capable of preventing air from escaping from the mold surface of the punch, which is generated at the time of injection filling.
An injection mold for molding an information recording board, characterized by being formed on a rough surface of ˜100 μm.