JPH0421937A - Optical disk - Google Patents

Abstract

PURPOSE:To improve the adhesive property of a substrate consisting of plastics and an antistatic film contg. conductive fillers and to prevent the cracking of the film surface by forming the above-mentioned film on the surface of the substrate on the side on which a laser beam is made incident. CONSTITUTION:A recording film 2 for magneto-optical recording is formed on one surface of the substrate 1 consisting of the plastics, such as polycarbonate and acrylic. A UV curing resin of an acryl urethane system is then applied on this film 2 and a UV curing resin of an acryl urethane system contg. the conductive fillers of the fine particles of tin oxide having 0.2mum average grain size is applied on the surface opposite therefrom. The resins on both surfaces of the substrate 1 are irradiated with UV rays and are thereby cured to form a protective film 3 and the antistatic film 4. The film 4 side is irradiated with the laser beam. The sticking of dust on the substrate surface is prevented, by which the adhesive property of the substrate 1 and the film 4 is improved and the cracking of the film 4 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disk in which an antistatic film is formed on a substrate.

[Conventional technology]

As the demand for optical discs increases, one major problem is dust and the like that adhere to the disc surface due to charging or the like. In other words, this dust and the like can cause laser beam mistracking or errors when using an optical disc, degrading the characteristics of the optical disc and preventing its performance from being fully demonstrated. Therefore, the need for an antistatic film on the surface of an optical disk is increasing. Therefore, as shown in FIG. 2, an optical disk is currently used in which an antistatic film 8 is formed on the laser beam incident surface side of a substrate 5 on which a recording film 6 and a protective film 7 are formed. After forming a recording film 6 on one side of the substrate 5 and further forming a protective film 7 on it, a surfactant-based or siloxane-based resin with an antistatic effect is applied to the other side of the substrate 5. The antistatic film 8 is formed by applying it uniformly using various methods such as a spin code, and irradiating it with ultraviolet rays or the like if necessary.

Further, in order to prevent performance deterioration of the optical disc by wiping the disc surface even when dust is attached, it is desirable that the antistatic film 8 has the performance of both preventing static electricity and improving surface hardness.

[Problem to be solved by the invention]

Most of the antistatic films 8 currently in common use are those based on the above-mentioned surfactants and siloxanes.

However, in surfactant-based antistatic films made by mixing surfactants into UV-curable resins, etc., if the proportion of surfactants mixed is high, the antistatic effect is large, but the surface hardness is not sufficient, and the surface activity If the mixing ratio of the agent is small, the surface hardness will improve, but the antistatic effect will be reduced. That is, since antistatic performance and surface hardness improvement performance are contradictory, it is necessary to select the optimum mixing ratio of the surfactant.

Furthermore, in optical discs on which a surfactant-based antistatic film is formed, under high temperature and high humidity environmental conditions such as 80°C and 90% relative humidity, the surfactant oozes out from the surface or the oozed surfactant There is a problem with long-term stability because water may adhere to the surface and form water droplets.

On the other hand, siloxane-based antistatic films have good antistatic performance and are hard, but the film thickness is 0.2 μm.
m or less and the film thickness cannot be increased, so when used on the substrate 5 made of soft plastic, there is a problem that sufficient surface hardness cannot be obtained. Furthermore, when a low-temperature-high-temperature cycle test is performed on an optical disk on which this siloxane-based antistatic film is formed, cranks may occur on the surface due to poor adhesion between the plastic substrate and the film.

[Means to solve the problem]

In order to solve the above-mentioned problems, an optical disc according to the present invention is an optical disc having a substrate made of plastic, and an antistatic film is formed on the surface of the substrate on which the laser beam enters, The antistatic film is characterized by containing a conductive filler.

[For production]

According to the above configuration, the antistatic film contains a conductive filler and can have a film thickness of several micrometers, so that the surface electrical resistance is reduced and the surface hardness is improved. Also,
Even if the antistatic film is placed in a high-temperature, high-humidity environment, the conductive filler will not ooze out or otherwise change over time, ensuring long-term stability. Furthermore, even if a high temperature/low temperature cycle test is performed, no cracks will occur on the surface of the antistatic film.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

As shown in FIG. 1, the optical disc of this embodiment has a substrate 1 made of plastic such as polycarbonate or acrylic.
For example, Affi N/DyFeCo/
All! N/A/! A recording film 2 such as a magneto-optical recording film consisting of
is formed. Further, on this recording film 2, a protective film 3 made of an acrylic urethane-based UV curing resin or the like is formed. On the other hand, on the surface of the substrate 1 opposite to the surface on which the recording film 2 is formed, an acrylic urethane-based UV irradiator containing a conductive filler of tin oxide fine particles with an average particle size of 0.2 μm is used.
An antistatic film 4 made of cured resin is formed to have a thickness of about 2 μm.

When this optical disk is loaded into an apparatus and recording, reproduction, etc. are performed, an optical pickup accesses the side of the substrate 1 on which the antistatic film 4 is formed and irradiates it with laser light.

In the above configuration, a method of manufacturing the present optical disc will be described below.

First, the recording film 2 is formed on one surface of the substrate 1.

Next, an acrylic UV curing resin that will become the protective film 3 is applied onto the formed recording film 2. On the other hand, on the surface of the substrate 1 opposite to the surface on which the recording film 2 is formed, an acrylic UV curable resin mixed with a conductive filler and which is the same as the resin used for the protective film 3 is applied. Furthermore, the UV curing resin coated on both surfaces of the substrate 1 is cured by irradiating ultraviolet rays to obtain a protective film 3 and an antistatic film 4.

Table 1 shows the physical properties of the optical disk obtained as described above and the conventional optical disk.

Table 1 As shown above, the obtained optical disk has improved surface hardness and lower surface resistivity compared to conventional optical disks, and therefore has improved antistatic effect. Furthermore, since it does not contain a surfactant, the surfactant will not ooze out even under high temperature and high humidity environmental conditions. Furthermore, since the substrate 1 and the UV cured resin have good adhesion, surface cracks do not occur when a high temperature-low temperature cycle test is performed.

Moreover, with the above structure, the protective film 3 and the antistatic film 4 can be cured at the same time, and there is no need to form the protective film 3 and the antistatic film 4 separately as in the conventional example.

Note that the protective film 3 and the antistatic film 4 may be cured separately as in the conventional case, and in that case, the UV curing resins used may not be the same.

Further, in this example, tin oxide fine particles were used as the material of the conductive filler, but other materials such as zinc oxide, antimony oxide, vanadium oxide, ITO (Indium Ti
n 0xide) etc. may also be used.

〔Effect of the invention〕

As described above, in the optical disc according to the present invention, since the antistatic film contains a conductive filler, the surface resistance is reduced, and as a result, it is possible to prevent dust from adhering to the substrate surface of the optical disc. Furthermore, since the film thickness can be made several micrometers, the surface hardness of the antistatic film is improved.

In addition, even if the antistatic film is placed in a high temperature and high humidity environment, the conductive filler does not ooze out or change over time, ensuring long-term stability.

Furthermore, even if a high temperature/low temperature cycle test is performed, since the plastic substrate and the antistatic film have good adhesion, no cranking will occur on the surface of the antistatic film.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention, and is a longitudinal sectional view showing the structure of an optical disc. FIG. 2 shows a conventional example of the present invention, and is a longitudinal sectional view showing the structure of an optical disc. 3 is a substrate, 3 is a protective film, and 4 is an antistatic film. Patent applicant Sharp Corporation] Figure 1

Claims (1)

[Claims] 1. An optical disc having a substrate made of plastic and having an antistatic film formed on the surface of the substrate on which laser light enters, the antistatic film containing a conductive filler. An optical disc characterized by: