JPS59106937A - Preparation of information disc by duplication - Google Patents

Abstract

PURPOSE:To prevent air bubbles from mixing in molded resin while preventing the adhesion of foreign matters to the resin surface, in a forming molding method using radiation curable resin, by continuously performing a process reaching film formation after preliminary curing under a pressure reduced environment lower than the atmospheric pressure. CONSTITUTION:All of air lock chambers 1, 3, 5, a molding chamber 2 and a vacuum plating chamber 4 are formed in an air-tight structure and mutually partitioned by gate valves 6-11 while the chambers 1-5 are held under a pressure reduced state by vacuum pumps 17, 18. A base plate having a radiation curable resin layer formed to the surface thereof by a rotary coating apparatus 26 receives the irradiation f a minute amount of radiation from a radiation source 32 to perform the preliminary curing of the resin layer. Subsequently, the base plate is carried onto the exposure table 34 of an exposure apparatus 33 and the information signal of a mold surface is transferred to the surface of the resin layer by a mold 35 while the resin layer is perfectly cured by irradiating the same with radiation from a radiation source 37. Thus obtained duplicated information disc is introduced into a vacuum plating chamber 4 to form a film on the surface of the resin layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing copies of information discs such as video discs and digital audio discs.

[Technical background of the invention and its problems]

Conventionally, known methods for producing copies of information discs include combination molding, injection molding, and cast molding. In the compression molding method, the mold stamper has a structure that can be heated and cooled, a thermoplastic resin heated to above its melting point is placed in the mold, the mold is kept at a high temperature, and the resin is pressurized to high pressure to form the mold. This method hardens the molded resin body in a cooling cycle to obtain a duplicate disk. In the injection molding method, a duplicate disk is obtained by injecting a thermoplastic resin that has been melted and plasticized at high temperature and high pressure into the cavity of a mold. These compression molding methods and injection molding methods have excellent productivity, but the transfer of information signals from the unevenness on the mold to the replica disk is not accurate, and the manufacturing process is difficult because they are manufactured under high temperature and high pressure. It has drawbacks such as large-scale and expensive equipment.

On the other hand, although the cast molding method has the advantage of high transfer accuracy, cast molding using a normal thermosetting resin has a long curing time of several hours or more, resulting in extremely low productivity. On the other hand, casting resin is hardened by irradiation with radiation such as ultraviolet rays and electron beams.
In recent years, it has been discovered that the use of so-called radiation-curable resins reduces the molding time to the same level as compression molding and injection molding, requires relatively inexpensive manufacturing equipment, and has excellent transfer accuracy for duplicate disks. It has attracted attention.

A method for producing copies of information discs using radiation-curable resin is described in Japanese Patent Publication No. 53-33244, in which a mold is coated flat with liquid molding resin, a base is pressed against the mold, and a presser plate is further applied. After pressurizing the molded resin layer until it reaches a predetermined thickness, the υ resin is cured by radiation irradiation, and the hardened molded resin layer is peeled off from the mold to obtain a duplicate disk, in particular. A radiation-cured resin is dropped onto a mold as described in 1983-116105, and a base deformed into a convex spherical shape is pressed onto the resin, and the resin is stretched flat on the mold, or A method of obtaining a duplicate disk by applying suction between the mold and the base over the entire circumference while holding down the resin with a base deformed into a convex spherical shape, stretching and spreading the resin, curing it by irradiation with radiation, and peeling it off, JP-A-55 -15
The mold and base described in 2028 are placed facing each other, a radiation-cured resin is injected into the gap between the two, the thickness of the resin layer is reduced to a predetermined thickness by suppression, and then the radiation-cured resin is A method of obtaining a duplicate disk by curing and peeling by irradiation,
Furthermore, a method is known in which a resin layer is uniformly formed on a mold by applying pressure to a base with a roller.

One of the problems when manufacturing duplicate disks using the cast molding method is the inclusion of air bubbles in the cast molding resin. Air bubbles mixed in the resin can cause information signal loss, or so-called dropout, to occur on non-contact playback discs, such as optical video discs and digital audio discs (5D system), which can impair image and sound quality. On the other hand, contact playback discs, such as V
In a capacitive video disc such as an HD system, air bubbles on the surface form recesses, which similarly cause dropouts and breakage of the playback needle. For this reason, it is clear that the inclusion of air bubbles in the molded resin layer must be avoided at all costs in any disc of any playback method. The size of the problematic bubbles depends on the recording density of the information signal, but in the above example, bubbles as small as about 1 μm can cause dropouts.

Furthermore, another problem is the attachment of foreign matter (dust, etc.) to the information signal surface. Like air bubbles, this causes dropout, but unlike air bubbles, the defect can be eliminated by removing it from the surface. However, for non-contact playback discs, it is essential to form a reflective coating on the molded resin layer, so foreign matter that adheres to the information signal surface between the casting process and the reflective coating forming process can be removed. Impossible to remove, resulting in permanent dropout. This is a similar problem in contact playback type discs, such as capacitive type discs, especially in so-called coated disc structures in which a dielectric thin film is formed on a conductor.

[Purpose of the invention]

The purpose of the present invention is to prevent air bubbles from being mixed into the molded resin during the production of replicas of information disks by the cast molding method using radiation-cured resin, and to prevent the formation of a film on the resin surface after the cast molding. It is an object of the present invention to provide a method for producing a copy of an information disc, which prevents foreign matter from adhering to the resin surface that occurs during production, thereby making it possible to obtain copies of information discs with fewer dropouts.

[Summary of the invention]

In the present invention, a radiation-cured resin layer is provided on a substrate, and this is pre-cured by irradiation with a small amount of radiation to improve the viscosity and decrease the volatility of the resin layer, and then the resin layer is depressurized from atmospheric pressure. The resin layer is brought into contact with a mold under a controlled environment to transfer the unevenness information signal on the mold surface, then the resin layer is completely cured by irradiation with radiation, and then a film is formed on the resin layer using a vacuum plating method. In particular, it is characterized in that the steps from preliminary curing to film forming cloth are carried out continuously in an environment reduced from atmospheric pressure.

〔Effect of the invention〕

According to the present invention, the generation of air bubbles due to air entrainment that occurs when the surface containing the information signal consisting of the unevenness of the mold is brought into contact with the surface of the radiation-cured resin layer on the base in the atmosphere to transfer the information signal is prevented. , can be reduced or prevented by performing the transfer under reduced pressure. The information signal surface formed by the transfer of the duplicate information disk remains in a clean environment under reduced pressure after being peeled off from the mold until the film formation on the surface is completed.
There is less chance of contamination such as foreign matter adhesion, and therefore, a high-quality duplicate disc with less muddy lag-out can be easily obtained.

[Embodiments of the invention]

The figure is a sectional view of a blank manufacturing apparatus for explaining an embodiment of the information disk duplication manufacturing method according to the present invention. In the figure, aerodynamic chambers 1, 3, and 5, a molding chamber 2, and a vacuum plating chamber 4 all have an airtight structure and are separated from each other by valves 6-11. The first airlock chamber 1 and the molding chamber 2 are connected by a vacuum bomb f17 via a nozzle 12-13, and the second and third airlock chambers 3 and 5 and the vacuum plating chamber 4 are connected to the pulp 1
4 to 16, each can be brought into a state of being reduced from atmospheric pressure by a vacuum bomb f18. Reference numerals 19 to 21 designate storage cassettes capable of storing a plurality of substrates and disks, and the disks are held within these cassettes so as not to damage the information signal surface. Furthermore, these cassettes have a structure that allows them to be easily attached and detached from the main body of the apparatus. 22-25
indicates the transport mechanism for the duplicate disk.

An example of a molding process using this device is shown below. Usually, each chamber 1-5 has a pump 17. It is maintained under reduced pressure using Ig.

First, one substrate is mounted and fixed on the turntable 27 of the rotary coating device 26 and rotated, and radiation curing resin is supplied from the resin tank 28 to the nozzle 31 through the dust removal filter 29 and the bomb fso, and the radiation is applied onto the substrate. Forms a uniform thin layer of cured resin.

The radiation-curing resin referred to here can be any type of resin as long as it is cured by the action of radiation, such as ultraviolet rays, electron beams, gamma rays, etc., but in terms of safety, productivity, handling, etc. It is particularly preferable to use an ultraviolet curing type acrylic paint as the curing resin. In addition, this resin is usually in a liquid state, and if the resin contains a large amount of bubbles or dissolved gas, it will foam after being formed as a thin layer on the substrate, causing defects, so it should be prepared in advance under reduced pressure. It is advisable to vacuole.

In this way, a radiation-cured resin layer is formed on the surface of the base.
The resin layer is precured by irradiation with a minute amount of radiation from the radiation source 32. This pre-curing is
In addition to improving the viscosity of the radiation-cured resin layer and improving subsequent handling, it also reduces the volatility of the resin to prevent changes in the resin composition due to the volatilization of low-boiling components in the resin generated from the resin surface under reduced pressure. and equipment due to the adhesion of volatile matter,
This is to prevent contamination of the equipment.

Particularly, this preliminary curing is extremely effective when using a low viscosity resin because it facilitates preliminary defoaming.

If the degree of pre-curing is too low, the above effects will not be obtained;
Furthermore, if the pressure is too strong, the information signal due to unevenness will not be transferred sufficiently during the subsequent transfer process, and in severe cases, the mold will be damaged, so it must be controlled appropriately. When the above-mentioned ultraviolet curable acrylic paint is used as the radiation curable resin, preliminary curing requires 10% of the energy required for complete curing.
It is appropriate to apply about 50% of the amount from 100% to 50% of the total amount of water. However, if the resin is a lanocal polymerization type, and if curing is delayed due to curing inhibition due to oxygen in the atmosphere, irradiation should be performed in a nitrogen atmosphere or the above limit should be applied. It is necessary to irradiate large amounts of ultraviolet rays.

The substrate whose resin layer has been precured is stored in the cassette 19 by the transport mechanism 22. At this time, the first air chamber 1 is opened to the atmosphere by the pulp 12, and the r-) pulse chamber is also in an open state. A predetermined number of substrates are placed in the cassette 19.
After storing it in? -) Close the pulp 6, switch the pulp 12 to the vacuum pump 17 side, and change the first aerodynamic chamber 1 to the molding chamber 2.
After equalizing the pressure, open the r-top valve 7. Next, the substrate whose resin layer has been precured is transported from the cassette 19 to the exposure table 34 of the exposure device 33 by the transport mechanism 23. Then, a mold 35 having an information signal consisting of irregularities on the surface opposite to the resin layer surface is brought into contact with the radiation-cured resin layer by a cylinder 36 and pressed, thereby transferring the information signal on the mold surface to the resin layer surface. The radiation curable resin layer to which this information signal has been transferred is irradiated with radiation from the radiation source 37, passing through the exposure table 34 and the base, to completely cure the resin layer and integrate it with the base.

As for the radiation used for this complete curing, as in the preliminary curing,
It is preferable to use ultraviolet light, and the light source is preferably a near-ultraviolet mercury lamp, a chemical lamp, etc. In that case, the substrate and the exposure table 34 are made of acrylic resin, I-liquor nate resin, acrylonitrile, etc., which are substances that transmit ultraviolet light. - It is suitable to use glass such as styrene copolymer resin, blue plate, Pyrex, etc.

After complete curing by radiation irradiation, the cylinder 36 is driven in the opposite direction to release the mold 35 from the completely cured resin layer integrated with the base. The thus obtained duplicate information disk is stored in the cassette 2o in the second airlock chamber 3 by the transport mechanism 24. At this time, the second airlock chamber 3 and the molding chamber 2 are at equal pressure, and f-) It is thermal theory that the pulp 8 is open.

The subsequent steps may be a so-called in-line vacuum plating process with a vacuum stock chamber.

In this embodiment, an example in which a vacuum evaporation method is used for this vacuum plating process will be described.

That is, a predetermined number of duplicate information disks are placed in the cassette 20.
f-) Close the pulp 8 and operate the pulp 14 to equalize the pressure of the second air chamber 3 with the vacuum plating chamber 4, and then open the dirt pulp 9. In this state, the duplicate information disks are introduced into the vacuum plating chamber 4 one by one from the cassette 20 by the transport mechanism 25, and a film of material evaporated from the evaporation source 38 is continuously formed on the surface of the radiation-cured resin layer of the disk. After that, it is stored in the cassette 21.

The term "vacuum plating method" as used herein refers to film forming methods that are carried out in an environment with reduced pressure below atmospheric pressure, such as vacuum evaporation method, snokstering method, ion derating method, and plasma CVD method. When forming an aluminum film as a reflective film on an audio disc, vacuum deposition or sputtering is preferred from the viewpoint of ease of handling, film properties, maintainability, and the like.

After applying vacuum plating to all the duplicate information disks in the cassette 20 and storing them in the cassette 2, the dirt pulp 10
The nozzle 16 is opened to the atmospheric pressure, the third airlock chamber 5 is returned to the atmospheric pressure, and the date pulp 11 is opened to obtain the coated duplicate information disk stored in the cassette 21.

In addition, in the above example, the higher the degree of vacuum in the molding chamber 2, the less air bubbles are entrained, but the low boiling point components contained in the radiation-cured resin are volatilized and distilled out, causing a change in the resin composition and causing damage to the equipment in the molding chamber. It will pollute. To prevent this, usually (1) reduce the degree of vacuum in the molding chamber;

(2) Use a cured resin made of components with low volatility.

There are two methods. However, method (1) increases air bubble entrainment, and method (2) usually uses a resin with a high molecular weight, resulting in high viscosity, making it extremely difficult to remove air bubbles once mixed in the resin, that is, to pre-defosolize. As a result, the duplicated disk will also contain air bubbles. On the other hand, in the present invention, it is possible to improve the viscosity and reduce the volatility by pre-devesulating the resin at a low viscosity, coating it on the substrate, and then pre-curing it, thereby improving the viscosity and reducing the volatility. Therefore, the amount of pressure reduction in the molding chamber 2 is preferably in the range of 30 to 76 tm Hg, particularly preferably in the range of 40 to 65 cm Hg.

On the other hand, the amount of pressure reduction in the vacuum plating chamber 4 may be the same as when vacuum plating is performed by a conventional method.In the present invention, since disk molding and vacuum plating are consistently performed under reduced pressure, the pressure reduction in the molding chamber 2 is reduced to a vacuum. It can be thought of as equivalent to the roughing (preliminary depressurization) step of the plating process, and the structure is simpler than when the molding process and vacuum plating process are performed separately, and the power cost required for depressurization in the process is reduced. It has the advantage of significant savings.

[Brief explanation of the drawing]

The figure is a cross-sectional view of an information disk duplication manufacturing apparatus for explaining an embodiment of the present invention. 1... First aerodynamic chamber, 2... Molding chamber, 3...
2nd aerodynamic chamber, 4... Vacuum plating chamber, 5... 3rd aerodynamic chamber, 6-11... f-) valve, 12-
16...Pulp, 17.18...Vacuum pump, 19
~21...Storage cassette, 22-25...Transport mechanism, 26...Rotary coating device, 27...Turn chisol, 28...Radiation curing resin tank, 29...Dust removal filter, 30...・Pressure bonder, 31... Nozzle, 3
2.37... Radiation source, 33... Exposure device, 34...
...Exposure table, 35...Mold, 36...Cylinder, 3
8... Evaporation source, 39... Power source for evaporation source, 40...
Pollution prevention wall.

Claims (2)

[Claims] (1) In a method of producing copies of information discs by casting using radiation-curable resin, the first step is to provide a radiation-curable resin layer on a substrate, and to pre-cure this resin layer by irradiating it with a small amount of radiation. A second step is to transfer the information signal by bringing a mold having an information signal made of unevenness into contact with the surface of the pre-cured resin layer, and a third step is to expose the resin layer to which the information signal has been transferred to radiation. It comprises a fourth step of completely curing the resin layer by irradiation, and a fifth step of forming a film on the surface of the completely hardened resin layer by vacuum plating, and from the third step to the fifth step the pressure is reduced from atmospheric pressure. A method for producing copies of information discs, characterized in that the production is performed continuously under a controlled environment. (2) The method for manufacturing copies of information discs according to claim 1, wherein the amount of pressure reduction relative to the atmospheric pressure of the environment in which the second and third steps are performed is 30 to 76 cm Hg.