JPH03105740A - Formation of rugged pits - Google Patents

Abstract

PURPOSE:To prevent the intrusion of bubbles and to allow the effective discharge of the bubbles by applying a radiation curing type resin on both of a transparent substrate or supporting sheet and a stamper having rugged pits stored with prescribed information. CONSTITUTION:The stamper 10 having the rugged pits stored with the prescribed information near a transfer region B is supported on a holder 11 and is so formed that the stamper can move back and forth to and from the transfer region B. A spray head 12 is disposed below the stamper 10 so that the radiation curing type resin similar to the radiation curing type resin to be applied on the transparent substrate 1 is applied on the rugged pit surface of the stamper 10. This stamper 10 is introduced into the transfer area B where a pressure contact operation is executed by a press-contact roller 5. The transparent substrate 1 is irradiated with UV rays from the lower side thereof by a UV irradiation lamp 6 and the curing of the radiation curing type resin is executed. Thus, the intrusion of the bubbles and the contamination of the stamper occurring therein are prevented and the productivity is improved.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for forming uneven pits in optical discs such as compact discs (CDs) and laser video discs (LVDs), and particularly relates to a method for forming uneven pits in optical discs such as compact discs (CDs) and laser video discs (LVDs).
This invention relates to a method for determining the shape of uneven pits using the 2P method.

(Prior Art) As a method for manufacturing optical discs, a photo polymer method is known in which a disc is manufactured using a polymer or a combination thereof (ultraviolet curable resin) that is cured by ultraviolet irradiation.

That is, in this method, an ultraviolet curable resin is applied between a stamper (mold) having uneven pits in which predetermined information is stored and a transparent substrate that serves as the disk base material, and ultraviolet rays are irradiated to print the desired information. After the resin is cured, it is peeled off from the stamper to form a recording layer with uneven pits on the transparent substrate.
A metal reflective film is formed on the uneven pit surface by means such as metal vapor deposition or sputtering, and a protective film is further formed thereon to form an optical disc.

However, in the above-mentioned photopolymer method, air bubbles are likely to be mixed into the ultraviolet curable resin layer, resulting in problems such as signal errors and poor curing of the ultraviolet curable resin. In particular, when curing failure of the ultraviolet curable resin occurs, inconveniences such as staining of the stamper occur, which necessitates cleaning work and significantly reduces productivity.

In order to avoid the inclusion of such air bubbles, for example, as shown in FIG.
are placed, a transparent substrate 52 is passed between the two, and the substrate 52
A known method is to pour the ultraviolet curable resin 53 onto the stamper 50 while bending the end of the stamper 50 upward, and move the pressure roller 51 forward to apply pressure from the end of the stamper 50.

According to such a means, air bubbles mixed into the ultraviolet curable resin are discharged from the open portion side according to the difference between the pressure at the time of crimping and the outside air pressure.

(Problem to be Solved by the Invention) However, in the prior art method as described above, even though air bubbles are effectively discharged when the advancing speed of the pressing roller 51 is low, the advancing speed of the pressing roller 5l is When the speed becomes high (for example, 3 m/sin or more), air bubbles that are mixed in due to the wraparound of the ultraviolet curable resin 53 during the crimping operation adhere to the transparent substrate 52 or the stamper 50, making it difficult to remove them. Problems such as poor resin curing and signal errors are likely to occur.

Therefore, an object of the present invention is to provide a structure for forming uneven pits that effectively prevents the inclusion of air bubbles or discharges air bubbles even when the advancing speed of the pressure roller is set to a high speed, thereby making it possible to manufacture optical discs with high productivity. Its purpose is to provide a method of formal precepts.

(Means for Solving the Problems) According to the present invention, a radiation-curable resin is applied onto a transparent substrate or a support sheet, and a radiation-curable resin is also applied onto a stamper having uneven pits in which predetermined information is stored. A resin is applied, and the transparent substrate or support sheet is pressed against the stamper in a positional relationship such that the radiation-curable resins are in contact with each other. In this state, ultraviolet rays are irradiated from the transparent substrate or support sheet side to remove the radiation. A method for forming uneven pits is provided, which comprises curing a curable resin to transfer uneven pits, then peeling off a stamper, and then forming a metal reflective film on the surface of the uneven pits.

An important feature of the method of the present invention is that a radiation-curable resin is applied to both the transparent substrate or support sheet and the stamper having concavo-convex pits in which predetermined information is stored.

In other words, by adopting the above-mentioned means,
Even if air bubbles are mixed in due to the radiation-curable resin wrapping around during the crimping operation, the air bubbles remain free from the transparent substrate, support sheet, or stamper.
This effectively prevents air bubbles from adhering to the transparent substrate, support sheet, or stamper, and allows the air bubbles to be effectively discharged.

For example, as is clear from the examples described later, when the radiation-curable resin is applied only to the transparent substrate or support sheet, the stamper is contaminated when the pressure roller travels at a speed of 2.4 m/win. On the other hand, when the radiation-curable resin is applied to both the transparent substrate or support sheet and the stamper, the stamper is not contaminated even when the pressure roller travels at a speed of 7.2 m/+in.

The method of the present invention will be explained below based on specific examples shown in the accompanying drawings.

In FIG. 1, which shows an example of an apparatus for suitably carrying out the method of the present invention in which a transparent substrate is used, a transparent substrate l passes from a film sublime roller 2 through a coating area A and a transfer area B, and then passes through a final coating area A and a transfer area B. It is adapted to be wound up by a take-up reroller 3.

A coating head 4 is provided in the application area A,
A radiation curing type is applied to one side of the transparent substrate l.

Further, in the transfer area B, a pressure roller 5 is provided, and an ultraviolet ray irradiation lamp 6 is arranged, so that ultraviolet rays are irradiated from the lower side of the transparent substrate 1.

Further, in the vicinity of the transfer area B, a stand bar 10 having uneven pits in which predetermined information is stored is supported by a holder 11. This stamper 10 is capable of reciprocating movement between it and the transfer area B.

Further, a spray head l2 is disposed below the stamper 10, and the radiation-curable resin similar to that applied to the transparent substrate l is applied to the uneven pit surface of the stamper 10. There is.

That is, according to the present invention, a stamper 10 whose uneven pit surface is coated with a radiation-curable resin is introduced into the transfer area B, where a pressing operation is performed by the pressing roller 5. The pressure bonding strength of the pressure roller 5 varies depending on the viscosity of the radiation-curable resin used, but is, for example, 700 cps (25°C).
In this case, it is about 180 to 220 g per lcm width.

In this state, ultraviolet rays are irradiated from the lower side of the transparent substrate 1 by the ultraviolet irradiation lamp 6 to cure the radiation-curable resin. The curing of radiation-curable resins performed by ultraviolet irradiation is usually completed within a few seconds. After curing,
The stand bar 10 returns to its initial position, and at this time, the cured radiation-curable resin is peeled off from the stand bar 10 together with the transparent substrate 1, and the uneven pit surface on which predetermined information is stored is exposed on the transparent substrate 1. transcribed into.

Next, the transparent substrate i to which the uneven pit surface has been transferred is fed by one transfer distance, and the above steps are repeated again.

In the method of the present invention described above, it is preferable that the radiation-curable resin layer coated on the transparent substrate 1 generally has a thickness of 10 to 50 μm, and the thickness of the stanbar 10
The layer of radiation-curable resin applied to the uneven pit surface of
Generally, it is preferable to have a thickness of 1 to IO μm.

In addition, as a radiation-curable resin, Japanese Patent Application Laid-Open No. 6436615
For example, oligomers such as epoxy (meth)acrylate and urethane (meth)acrylate, monomers such as glycidyl (meth)acrylate, trimethylbrobantri(meth)acrylate, and acrylic acid, and a photopolymerization initiator. etc. can be used.

The viscosity of radiation-curable resin is usually 700 to 7000 cp.
s (25°C).

Further, as the transparent substrate 1, the thickness of polycarbonate resin, acrylic resin, vinyl chloride resin, etc. is usually 1 to 1.
A translucent plastic plate with a diameter of 5 mm, preferably 1.2 mm, is used, and a glass plate may also be used depending on the case.

The feed speed of the pressure roller is usually 0.5 to 61a/l.
lin, preferably 2.5 to 3 m/miri.

The transparent substrate 1 having an uneven pit surface obtained by the above-mentioned process is coated with a metal reflective film on the uneven pit surface by metal vapor deposition or sputtering according to a method known per se. A protective film is formed, and a disc is punched out to form an optical disc.

This metal reflective film is formed of, for example, aluminum, aluminum-titanium alloy, titanium-copper alloy, silver-titanium alloy, etc., and generally contains 500 to 1,500 pieces, especially 7
It has a thickness in the range of 00 to iooo.

Note that the optical disc obtained in this case has a transparent base Fi1
A laser beam is irradiated from the side, and the stored information is reproduced by the reflected light from the metal reflective film surface (hereinafter referred to as the "life training starting surface") on the side of the uneven binote surface.

The method of the present invention is a type in which a laser beam is irradiated from the side opposite to the transparent substrate 1, and the stored information is reproduced by the reflected light on the metal reflective film surface located on the opposite side from the starting surface. It is particularly advantageously applied to the production of optical discs.

An example in which the above process is applied to the manufacture of this type of optical disc will be briefly explained with reference to FIG.

That is, in the process shown in FIG. 1, uneven pits 20 are formed on the support sheet 25 in the same manner as described above except that the support sheet 25 is used instead of the transparent substrate 1, and the formed uneven pits 1 and 25 are formed. A metal reflective film 2l is formed on the surface 20 by means of metal vapor deposition or sputtering.
is formed (step ``A''). In this case, the raw starting side is represented by 21a and the opposite side is represented by 2lb. Further, the thickness of the metal reflective film, the metal composition, etc. may be the same as described above.

Next, a radiation curing resin 23 is applied to the surface of the metal reflective film 2l.
is applied, and a separately prepared transparent substrate 24 is bonded to this by pressing with a roller or the like. In this state, ultraviolet rays are irradiated from the side of the transparent substrate 24 to cure the radiation-curable resin 23 and form a transparent adhesive layer (23) (step "B").

The support sheet used in this example is a transparent resin sheet having a thickness of 25 to 100 microns, such as polycarbonate resin, acrylic resin, or polyester resin.

In addition, the radiation-curable resin used for forming the transparent adhesive layer can basically be similar to that used in the process shown in Figure 1, but the formed transparent adhesive layer is Since it is located on the optical path side, a particularly highly transparent material is used, and no coloring agent or the like is mixed therein.

In addition, this transparent adhesive layer 23 needs to be provided uniformly so as not to change the optical path length, and its thickness is 5 to 50 mm.
It is desirable that it be in the range of μ.

If the thickness is less than 5μ, pinholes will easily occur, and if it exceeds 50μ, it will be difficult to achieve a uniform thickness.

After forming the transparent adhesive layer, the support sheet 25 is peeled off if necessary, and a disk shape is punched out to obtain a single-sided readable optical disk. To read this optical disc, a laser beam or the like is incident from the transparent substrate 24 side, and the metal reflective film 24 is read.
This is done using the reflected light from the surface 2lb of 1. In this case, the peeled support sheet 25 is reused as appropriate.

The optical disc obtained in this way has a metal reflective film 21
Since the optical path for information reproduction is located on the surface 2lb side opposite to the recording start surface 21a, pit errors can be more effectively avoided and reproduced compared to conventional optical discs. It has the advantage that the quality of information (such as sound and images) is also good. In other words, in the conventional optical disc in which the optical path is located on the production or starting surface 21a side of the metal reflective film 2l, the surface reflectance of the concave portions and the surface reflectance of the convex portions in the uneven pits formed by the metal reflective film are considerably different. As a result, there are many pit errors, and the quality of the reproduced information is not fully satisfactory.

However, on the surface 2lb of the metal reflective film 2I opposite to the growth initiation surface 21a, the surface reflectance of the concave portions and the surface reflectance of the convex portions in the uneven pits are different due to the surface smoothing effect when forming the metal reflective film. Therefore, the above-mentioned advantages can be achieved in an optical disc in which the optical path for information reproduction is located on the surface 2lb side of the metal reflective film 21 opposite to the generation start surface 21a.

(Example) Using the apparatus shown in FIG. 1, a radiation-curable resin having a viscosity of 700 cps was applied to a thickness of about 30 μm on a polycarbonate film having a thickness of 100 μm. In addition, about 5 to 1 liters of the same radiation-curable resin as above was added to the stamper.
Spray coated with Oall thickness. Incidentally, the spray coating was performed by airless spraying in order to minimize the scattering of droplets.

In this state, the speed of the pressure roller is varied to press the stamper and the polycarbonate film substrate, and the resin is cured by irradiating ultraviolet rays for 0.5 seconds, forming uneven pits in which predetermined information is stored. was transcribed.

The various films obtained were evaluated for bubble generation and stamper contamination, and the evaluation results are shown in Table 1.

For comparison, a similar evaluation was also performed on a stamper in which uneven pits were transferred without applying any radiation-curable resin, and the evaluation results are also shown in Table 1.

The composition of the radiation-curable resin used is as follows. Eboxy acrylate 40 parts by weight (εA-1370 manufactured by Mitsubishi Yuka Fine Co., Ltd.) Trimethylolpropane triacrylate 12 parts by weight Tricyclodecanediyl dimethylene diacrylate 20.9 parts by weight Silicone acrylate oligomer 0.3 parts by weight Isobonyl acrylate 9 parts by weight part acrylic acid
13 parts by weight l-Hydroxycyclohexylphenylketone 2.5 parts by weight Penzylphenone 1.2 parts by weight fHls4-dimethylaminobenzoic acid 1.2 parts by weight Air bubbles and contamination evaluation was performed using a CD error meter to detect CI errors. This was done by measurement and was classified as follows.

○; Pit error rate 0 to 20 △; Visotro error rate 20 to 200 The resulting contamination of the stamper was effectively prevented, and productivity was significantly improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of an apparatus for suitably carrying out the method of the present invention, and FIG. 2 is a diagram for explaining an optical disc manufacturing method to which the method of the present invention can be advantageously applied. FIG. 3 is a diagram showing a conventional method for determining the shape of uneven pits. i---Transparent substrate, 5---One pressure contact roller, io
----- Stamper, 20 --- One uneven pit surface, 21
---One metal reflective film Figure 1

Claims (1)

[Claims] (1) A radiation-curable resin is applied onto a transparent substrate or a support sheet, and a radiation-curable resin is also applied onto a stamper having uneven pits in which predetermined information is stored, so that the radiation-curable resins are bonded to each other. The transparent substrate or support sheet and the stamper are pressed together in a positional relationship such that they face each other, and in this state, ultraviolet rays are irradiated from the transparent substrate or support sheet side to cure the radiation-curable resin and transfer the uneven pits. 1. A method for forming uneven pits, which comprises forming a metal reflective film on the uneven pit surface after removing the stamper.