JPH11283284A - Injection molding machine for optical recording medium substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a nozzle, in which resin stringing is prevented and a substrate having a superior double refractivity and a transfer characteristic is molded, by providing an injection nozzle with a nozzle temperature control section and making the volume of resin filler to be less than specified between the nozzle tip and the end of a first nozzle temperature control section. SOLUTION: A nozzle tip side heater 6A being a nozzle temperature control section, and a nozzle end side heater 6B are provided on an injection nozzle 1 which is mounted on an injection molding machine. The volume of resin filler located in an intranozzle resin passing hole 4 between the nozzle tip 1 and the middle position of the gap between the heaters 6A and 6B is set less than 1 cm<3> , preferably less than 0.4 cm<3> . This injection molding machine having the nozzle 1 injects a substrate material such as polycarbonate resin into the space of a mold to make a substrate having the thickness of less than 0.63 mm for an optical recording medium. Thus, resin stringing is prevented, the transfer characteristic is superior, the shape of a stamper is accurately transferred and the substrate having a good refractivity is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine for molding a substrate for an optical recording medium by injecting a resin material from an injection nozzle into a cavity of a mold.

[0002]

2. Description of the Related Art An optical recording medium has the characteristics of high density, large capacity, and non-contact with a recording / reproducing head, and is a compact disk for reproduction only, a video disk, a recordable optical disk, and a recording, reproducing, and erasing. Possible magneto-optical disks, phase change disks, etc. have been developed and put into practical use.

[0003] The substrate of such an optical recording medium is molded by an injection molding method or an improved injection compression molding method using an organic resin having excellent optical characteristics such as polycarbonate so that mass production is possible. . The optical recording medium is manufactured by stacking a recording layer, a reflective layer, a dielectric layer for optical interference, an organic film, and the like on the substrate by sputtering, vapor deposition, coating, or the like.

On these substrates, information such as data, recording format, address, track guide, etc.
It is recorded in advance in pits and the like. Such a substrate is manufactured by recording information in advance in the form of irregularities on a stamper and transferring the information by injection (compression) molding.

FIG. 1 and FIG. 2 are schematic views of the tip of a conventional heating cylinder including a nozzle portion. 1 in the figure is a nozzle,
2 is a cylinder head and 3 is a cylinder. Also,
Reference numerals 6, 7, and 8 denote heaters for controlling the temperature of each part. The resin passes through the hole 5 of the resin passage in the cylinder head, passes through the hole 4 of the resin passage in the nozzle, and is introduced into the sprue bush of the mold. At this time, the temperature of each zone is controlled by heaters 6, 7, and 8 to a set temperature by a thermocouple (not shown) embedded in each zone. The temperature of the resin passing through the hole and the temperature indicated by the thermocouple are not necessarily the same, but they are relatively related to each other, and the temperature condition can be controlled. As shown in FIG. 2, two heaters 6 (6A, 6B)
Some are divided into In this case, both can be constituted by separate thermocouples and a temperature controller.

[0006]

However, it is not easy to completely transfer the shapes of the pits and grooves formed on the stamper to the substrate by the injection (compression) molding. As the recording density has increased, the track pitch has become smaller, and the slopes of pits and grooves have become steeper, and the improvement of transferability has been an issue in an increasingly large molding process.

Further, in a new optical recording medium using a phase change type recording layer recently proposed, the thickness of the substrate is reduced to half of the conventional thickness of 0.6 mm, which is an even more important problem. The reason why the transferability becomes difficult when the substrate thickness is small is that
Since the distance to the mold surface is shortened, the resin temperature is increased to 1.1 while the resin moves from the inner circumference to the outer circumference in the mold cavity.
It may be reduced as compared with the case of a thickness of 2 mm. As a result, especially the transferability of the outer peripheral portion is reduced.

Conventionally, to improve the transferability, the resin temperature,
Methods of increasing mold temperature, injection speed, compression pressure, etc. have been taken. However, all have limitations from the viewpoint of other characteristics, molding stability, and equipment capacity. In particular, when the temperature of the resin is increased, when the sprue is pulled out of the mold, a so-called thread pulling phenomenon occurs in which the resin is pulled out from the tip of the nozzle and the thread is drawn to the rear part of the sprue. When this occurs, there is a risk of damaging the stamper and the mold by being sandwiched in the mold, stopping the take-out robot due to the end portion adhering to the substrate, and deteriorating the characteristics of the molded substrate due to remaining in the cavity. When the resin temperature is lowered to suppress stringing, not only transferability is lowered, but also birefringence which is an important property for reducing jitter is deteriorated. The present invention
In view of this situation, a nozzle for forming an optical recording medium substrate, which prevents the above-described stringing, has good transferability, accurately transfers the shape of the stamper, and has good birefringence. It is intended to find out.

[0009]

An injection molding machine for an optical recording medium substrate according to the present invention is an injection molding machine for molding a substrate for an optical recording medium by injecting a resin material from an injection nozzle into a space of a mold. The injection nozzle is provided with a nozzle temperature control unit, and the filling volume of the resin material in the nozzle is 1 cm from the nozzle tip to the end of the first nozzle temperature control unit.
It is characterized by being ³ or less.

That is, the stringing described above as a problem is
This is a phenomenon in which the resin drawn from the nozzle is connected to the rear of the sprue in a thread shape when the mold is opened. This is because when the mold is opened and the sprue is pulled out from the sprue bush, the resin is not cut between the mold and the nozzle when the tip temperature of the nozzle is high. In order to lower the transferability and the birefringence, it is necessary to increase the temperature of the resin, but as a result, stringing tends to occur. At this time, it is important to keep the tip of the nozzle at a low temperature at which the resin is easily cut.

Therefore, in the present invention, in order to obtain a substrate for an optical recording medium, which prevents stringing, has good transferability, accurately transfers the shape of a stamper, and has good birefringence, it is necessary to use a nozzle. Is 1 unit from the tip of the nozzle to the end of the first nozzle temperature control unit.
It must be less than cm ³ .

Here, the first temperature control section of the nozzle means a temperature control section (for example, a heater section) which is the most distal in the nozzle section. In the case where the temperature control unit provided in the nozzle unit is divided into a plurality with a gap therebetween, the time until the end of the first nozzle temperature control unit means that the time between the first nozzle temperature control unit and the next It is assumed that it is up to an intermediate position. For example, as shown in FIG. 2, when a heater as a nozzle temperature control unit is divided into two parts, 6A and 6B, with a gap therebetween, the period from the nozzle tip to the end of the first nozzle temperature control unit is the same as the nozzle tip control. From heaters 6A and 6B
Up to the middle position of the gap between. The filling volume of the resin material in the nozzle means the resin volume in the resin passage portion corresponding to the range.

In order to solve the above-mentioned problem, it is necessary that this volume is 1 cm ³ or less. In order to improve transferability and birefringence while preventing stringing, this volume is preferably small, and 0.4 cm ³ or less is more suitably used.

In molding a substrate of an optical recording medium, the thickness distribution of the substrate becomes important. That is, the parallelism and rigidity of the fixed board are important factors. As a result, a certain width of the fixed plate is required. As a result, the nozzle part tends to be longer,
The design of the nozzle becomes important. Particularly, in an optical recording medium such as a magneto-optical disc or a phase-change optical disc using a thin substrate (especially one having a thickness of 0.63 mm or less),
The amount of resin used for one shot decreases, and the design of the nozzle portion becomes very important. That is, the present invention is suitably used for an optical disk or the like using a substrate having a thickness of 0.63 mm or less.

Note that the optical recording medium in the present invention is a recording medium that reproduces at least information by light such as laser light. Specifically, there are a read-only compact disk, a video disk, a recordable optical disk, a rewritable magneto-optical disk, and a phase change disk.

As the resin material, a known organic resin such as a polycarbonate resin and an amorphous polyolefin resin as a substrate material of an optical recording medium can be applied. Among them, a polycarbonate resin is preferably used in view of optical characteristics and mechanical characteristics. Further, when the substrate is injection-molded in the present invention, an injection compression molding method can be used according to the required substrate characteristics.

[0017]

Example 1 An injection nozzle having a structure shown in FIG. 2 was attached to an injection molding machine (trade name “MO40D3H” manufactured by Nissei Plastics Industry Co., Ltd.). FIG. 3 shows a cross section of the tip of the nozzle. The length of the heater as the temperature control unit is 6m for 6A
m and 6B are 50 mm. The distance (L2) between the two heaters was 5 mm. The nozzle inner diameter (D1) from the tip to the temperature control unit is 1.8 mm, and the length from the nozzle tip to the tip of the nozzle temperature control unit, that is, the land length (L)
1) is 10 mm, nozzle inside diameter after temperature control part (D2)
Is 5 mm. At this time, the filling volume of the resin material in the nozzle is 0.19 cm ³ from the tip of the nozzle to the end of the first nozzle temperature controller.

Using this injection molding machine, the recording capacity is 2.6.
A GB phase change optical recording medium substrate (diameter 120 mm, substrate thickness 0.6 mm) was injection molded. Note that a polycarbonate resin (trade name “AD5503” manufactured by Teijin Chemicals Limited) was used as the resin material. At this time, the injection mold temperature was 123 ° C. on the movable side and 128 ° C. on the fixed side.
The temperature of the cutter and the sprue was 60 ° C. The injection speed was 200 mm / sec, and the molten resin was filled in the mold cavity. The filling time is between 0.10 and 0.11 seconds. The temperature of each temperature controller is controlled by the cylinder temperature controller 8
Is 380 ° C, and the cylinder head temperature controller 7 is 375
C., the temperature at the rear end side temperature control section 6B of the nozzle section was 350 ° C., and the temperature control section 6A at the front end side of the nozzle section was 250 ° C.

As a quantitative evaluation of the state of occurrence of stringing, the length of the thread connected to the rear of the sprue was measured, but was not present.

The birefringence is measured by a birefringence measuring device (trade name “ADR-200B” manufactured by Oak Manufacturing Co., Ltd.).
Was used. Anneal the molded substrate at 80 ° C. for 8 hours,
It was evaluated after stabilization. Birefringence (23r) at a radius of 23 mm and birefringence (58r) at a radius of 58 mm when the pulling direction is set to + in a single pass.
Was 5 nm and -10 nm, respectively.

The transferability was evaluated by using an atomic force microscope (trade name "SFA-300" manufactured by Seiko Denshi Kogyo Co., Ltd.) and determining the land height and land angle from the cross-sectional shape by the method shown in FIG. In FIG. 4, the land surface (L) and the groove surface (G)
Represents the land height. Also, c and d are L and G
, And the angle between d and a straight line connecting the intersections of the slopes with each other is defined as a land angle (θ). Since it is more difficult to secure the transferability on the outer periphery than on the inner periphery, the evaluation at 58r was performed. As a result, the land height was 69 nm and the land angle was 35 °. Samples of complete transfer prepared from this stamper by the glass / 2P method had 69 nm and 34 °, respectively, confirming that the shape of the stamper was completely transferred.

[0022]

[Embodiment 2] The length of the temperature control section 6A at the nozzle tip side is set to 1
0 mm, the length of the nozzle rear end side temperature control unit 6B is 50 m
m. Except for this, the substrate was molded under the same conditions as in Example 1. That filling volume of the resin material in the nozzle, between the nozzle tip to the first nozzle temperature controller ends were molded by 0.27 cm ^3. As a result, no stringing occurred, the birefringence 23r was 6 nm, the birefringence 58r was -12 nm, and the transfer property was a land height A of 69 n.
m and the land angle θ were 34 °, and good results were obtained.

[0023]

[Embodiment 3] The length of the temperature control section 6A at the nozzle tip side is set to 1
4mm, length of the nozzle rear end side temperature controller 6B is 45m
m. Except for this, the substrate was molded under the same conditions as in Example 1. That is, the filling volume of the resin material in the nozzle was 0.35 cm ³ from the tip of the nozzle to the end of the first nozzle temperature controller. As a result, no stringing occurred, the birefringence 23r was 10 nm, the birefringence 58r was -13 nm, and the transfer property was a land height A of 68 n.
m, the land angle θ was 33 °, and good results were obtained.

[0024]

[Embodiment 4] The length of the temperature control section 6A on the tip side of the nozzle section is set to 2
0 mm, length of the nozzle rear end side temperature controller 6B is 40m
m, the temperature of the nozzle part tip side temperature control part 6A was 270 ° C. Except for this, the substrate was molded under the same conditions as in Example 1. That is, the filling volume of the resin material in the nozzle is
Molding was performed at 0.47 cm ³ from the nozzle tip to the end of the first nozzle temperature controller. as a result,
Stringing occurs 1 cm, birefringence 23r is 10 nm, birefringence 58r is -14 nm, and transferability is a land height A of 68 n.
m, the land angle θ was 33 °, and good results were obtained.

[0025]

[Embodiment 5] The length of the temperature control section 6A on the tip side of the nozzle section is set to 3
0 mm, the length of the nozzle rear end side temperature control unit 6B is 30 m
m, the temperature of the nozzle tip side temperature controller 6A was 285 ° C. Except for this, the substrate was molded under the same conditions as in Example 1. That is, the filling volume of the resin material in the nozzle is
The molding was performed at 0.66 cm ³ from the nozzle tip to the end of the first nozzle temperature controller. as a result,
Stringing occurs 1 cm, birefringence 23r is 12 nm, birefringence 58r is -16 nm, and transferability is a land height A of 68 n.
m and the land angle θ were 34 °, and good results were obtained.

[0026]

[Embodiment 6] The length of the temperature control section 6A on the tip side of the nozzle section is set to 4
0 mm, the length of the nozzle rear end side temperature controller 6B is 20 m
m, the temperature of the nozzle portion tip side temperature control section 6A was 290 ° C. Except for this, the substrate was molded under the same conditions as in Example 1. That is, the filling volume of the resin material in the nozzle is
Molding was performed at 0.86 cm ³ from the nozzle tip to the end of the first nozzle temperature control unit. as a result,
Stringing occurrence is 2 cm, birefringence 23r is 16 nm, birefringence 58r is -18 nm, and transferability is land height A is 68 n.
m, the land angle θ was 33 °, and good results were obtained.

[0027]

Example 7 A substrate having a thickness of 1.2 mm was formed under the same conditions as in Example 1 except that the mold was changed in Example 1 and the nozzle used was the same as that used in Example 6. did. No stringing occurred, the birefringence was 15 nm or less, and the transferability was good. Thereby, it was confirmed that the selection range of the nozzle becomes wider as the plate thickness increases.

[0028]

[Comparative Example 1] The length of the nozzle tip side temperature control section 6A is set to 5
0 mm, length of the nozzle rear end side temperature controller 6B is 10m
m, the temperature of the nozzle portion tip side temperature control section 6A was 320 ° C. Except for this, the substrate was molded under the same conditions as in Example 1. That is, the filling volume of the resin material in the nozzle is
The molding was performed at 1.05 cm ³ from the tip of the nozzle to the end of the first nozzle temperature controller. as a result,
Stringing occurrence is 10 cm, birefringence 23r is 20 nm, birefringence 58r is -20 nm, and transferability is land height A is 68 n.
m and the land angle θ were 33 °, which was an undesirable result. In Comparative Example 1, when the temperature of the nozzle-part-end-side temperature control unit 6A was lowered below 320 ° C., the stringing was reduced, but the birefringence was large, and the transferability was poor.

[0029]

Comparative Example 2 In Example 1, the heater as the temperature control unit was changed to the single heater shown in FIG. That is, the nozzle was provided with a heater as a temperature control unit having a length of 65 mm starting from a position 10 mm from the nozzle tip. That is, the filling volume of the resin material in the nozzle is 1.3 from the nozzle tip to the end of the nozzle temperature control unit.
0 cm ³ . The temperature of the temperature control unit is 320
° C. The other conditions were the same as in Example 1, and the substrate was molded. As a result, stringiness was 25 cm, birefringence 23r was 21 nm, birefringence 58r was -22 nm, and transferability was unfavorable, with land height A of 68 nm and land angle θ of 34 °. In Comparative Example 2, when the temperature of the nozzle-part-end-side temperature control unit 6A is lowered below 320 ° C., the stringing becomes small, but the birefringence becomes large.
The only result was that the transferability deteriorated.

[0030]

Comparative Example 3 The mold was changed in Comparative Example 2, and the thickness was 1.
A 2 mm substrate was molded. The birefringence was 15 nm or less, and the transferability was good.
C. Strings having a length exceeding cm were generated, which was an undesirable result.

[0031]

As described above, the present invention is a nozzle capable of suppressing stringing and forming a substrate having excellent birefringence and transferability, thereby providing a stable and good optical recording medium substrate. Now you can get it.

[Brief description of the drawings]

Fig. 1 Tip of heating cylinder

[Fig. 2] Tip of heating cylinder

FIG. 3 is a cross section of the tip of the nozzle.

FIG. 4 Method for evaluating transferability

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle 2 Cylinder head 3 Cylinder 4 Resin passage hole in nozzle 5 Cylinder head resin passage hole 6, 7, 8 Heater 6A Nozzle tip side heater 6B Nozzle rear end heater D1 Nozzle inside diameter from tip to temperature control part D2 Temperature control part Subsequent nozzle inner diameter L1 Land length L Land surface G Groove surface A Land height θ Land angle c Line 10% below land height from land surface d Line 10% above land height from groove surface

Claims (3)

[Claims] In an injection molding machine for molding a substrate for an optical recording medium by injecting a resin material from an injection nozzle into a cavity of a mold, the injection nozzle is provided with a nozzle temperature control unit, and the resin material in the nozzle is provided. An injection molding machine for an optical recording medium substrate, wherein a filling volume is 1 cm ³ or less from a nozzle tip to the end of a first nozzle temperature control section. 2. The optical recording method according to claim 1, wherein the filling volume of the resin material in the nozzle is 0.4 cm ³ or less from the tip of the nozzle to the end of the first nozzle temperature controller. Injection molding machine for media substrates. 3. The optical recording medium substrate to be molded has a thickness of 0.63 mm or less.
3. An injection molding machine for an optical recording medium substrate according to any one of items 2.