JPS6330880B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an information recording member that optically records information by irradiation with laser light, and more specifically, from the viewpoints of dustproofing, scratchproofing, corrosion prevention, and high sensitivity, an organic polymer protective film is applied to a recording medium. The present invention relates to an optical recording member that enables stable recording, reproduction, and additional recording over a long period of time. Conventionally, this type of information recording member has a glass or plastic substrate 1 on which Te or Te is deposited, as shown in Fig. 1.
Basically, the recording medium 2 is vapor-deposited with Bi, Mn, etc., but to prevent the adhesion of dust and to
to prevent damage to the recording medium 2.
In order to prevent this from being oxidized by water vapor, oxygen, etc. in the air, it has recently been considered to provide a transparent organic protective film 3 thereon as shown in FIG. Although this organic protective film is generally inferior in corrosion protection to protective films made of inorganic thin films made of oxides of metalloid elements such as Bi, Be, and Si, it does (1) reduce the writing sensitivity of the recording medium; (2) By adjusting the thickness of the protective film, it is possible to eliminate information loss during writing and reading caused by dust adhering to the protective film. For this reason, Japanese Patent Application Laid-open No. 75523/1983 describes a recording member in which an organic polymer film is laminated onto a recording medium by adhesive or thermocompression bonding. However, in such a recording member, when writing is performed using a laser, there is no place for the evaporated gas of the recording medium to go, so a large amount of laser power is required for writing, and the shape of the recording bits is disturbed. Also, attempts have been made to apply coating resin as a protective film by dissolving it in a solvent, but such recording members also have various drawbacks. For example, a solution of polyvinylidene chloride, polyvinyl chloride, polyurethane, unsaturated polyester, silicone resin, etc. is applied onto the recording medium using a roll coater, spinner, applicator, etc. to form a protective film. In this case, the choice of solvent is limited. Furthermore, even if a solvent that does not dissolve the substrate is used, cracks and flow phenomena may occur in the recording medium 2, although only to a small extent. Furthermore, it is difficult to apply these solution-type resins with good surface accuracy using a spinner or the like, and it is difficult to write or read from the protective film side. Furthermore, the corrosion resistance of the recording medium 2 is limited because many small holes are generated due to volatilization of the solvent during drying after coating. Therefore, as a result of intensive research into the use of solvent-free paints such as UV-curable paints as a protective film, the present inventors discovered that UV-curable paints containing epoxy resins modified with unsaturated carboxylic acids as a base. By using the cured film as a protective film,
It has been found that an information recording member with excellent corrosion resistance and moisture resistance, high S/N ratio, long life, and high sensitivity can be obtained. Here, as the unsaturated carboxylic acid, acrylic acid, methacrylic acid, long chain unsaturated fatty acids having 5 or more carbon atoms, etc. can be used. It is also effective to form a cured film made of an ultraviolet curable paint into a two-layer structure in which a soft film is used as a base and a cured film is laminated on this. 3 and 4 show examples of the structure of the recording member of the present invention, 11 is a substrate made of glass, plastic, etc., 12 is a recording medium made of Te, Bi, Mn, etc., and 13 is a substrate modified with unsaturated carboxylic acid. This is a protective film made of a cured film of an ultraviolet curable paint containing an epoxy resin as a base resin. In FIG. 4, the protective film 13 is composed of a soft film 13 ₁ and a hard film 13 ₂ . In general, UV-curable paints consist of a base resin, which is a photosensitive oligomer, a photopolymerization initiator, a reactive diluent, and a polymerization inhibitor.
Through experiments conducted by the present inventors, it has been found that when an epoxy resin modified with an unsaturated carboxylic acid is used as the base resin, it exhibits excellent protective film characteristics for the recording member. That is, the paint is
Generally speaking, the same can be said of photocurable paints, but since no solvent is used, after application, the film can be cured by irradiating ultraviolet rays after it becomes a free surface. Therefore, it can be cured with good surface precision. At the same time, since the recording medium of the metal film is not changed by the solvent, a recording member with a protective film having an excellent S/N ratio and error rate can be obtained. The error rate refers to the probability of dropout occurrence when pinhole defects occurring in the recording medium and optical modulation due to unevenness of the protective film are viewed as dropout noise. Further, by using an ultraviolet curable coating material, the protective film can be cured in a single hour without performing high-temperature heat treatment, thereby improving manufacturing yield and throughput. On the other hand, the moisture resistance test also revealed that the paint is a long-life protective film material for recording members. This is because (1) it does not contain a solvent, so there is no formation of small holes due to solvent volatilization, which blocks the passage of oxidizing gases such as oxygen and water vapor in the air, and (2) unsaturated carboxylic acid. By containing the modified epoxy resin in the paint as a base resin, the adhesion between the paint film and the metal film that is the recording medium is improved. This is thought to be due to the fact that in the case of saturated fatty acids, the resulting coating film exhibits particularly little distortion due to heat history and humidity history, and thus the recording medium coated with this is physically very stable. In addition, in order to increase the sensitivity of the recording member, it is possible to make the protective film soft by changing the composition ratio of the components contained in the paint, but by making the protective film a two-layer structure consisting of a soft layer and a hard layer. A recording member excellent in both high sensitivity and scratch resistance can be obtained. Examples will also be described in detail below. Example 1 20 parts of epoxy acrylate as a base resin for an ultraviolet curable paint, 1 part as a reactive diluent,
A mixture of 30 parts of 6-hexanediol diacrylate, 40 parts of trimethylolpropane triacrylate, and 7 parts of benzophenone and 3 parts of acetophenone as a photopolymerization initiator was prepared. The resulting UV-curable paint () was applied using a spinner onto an acrylic substrate on which Te was deposited, and cured by UV irradiation to form a 20μ
A recording member with a protective film of m was prepared. Ultraviolet irradiation was carried out under three 80W/cm concentrating ultraviolet lamps.
The test was carried out under the conditions that the sample was passed through at a speed of m/min. The surface precision of the protective film of this recording member was very excellent, and microscopic observation showed that no change in the recording medium was observed when the paint was applied. Therefore, when we applied a He-Ne laser to the protective film side of this recording medium and investigated the noise during reading, it was found to be very small (S/N ratio 40 dB), and it was difficult to write.
This was possible at 10mW and 500nsec, making it a highly sensitive recording medium. Even when this recording member was placed in a constant temperature and humidity chamber at a temperature of 50°C and a humidity of 90% for 15 hours to conduct an accelerated humidity resistance test, neither oxidation of the recording medium Te nor blistering of the protective film was observed. Almost no increase in error rate was observed before and after the accelerated test. This is thought to be because the adhesion of this coating film to metal is very excellent, and the moisture permeability and water content are quite low. Example 2 A paint in which the components of the ultraviolet curable paint prepared in Example 1 were changed to 60 parts of epoxy acrylate, 10 parts of 1,6-hexanediol diacrylate, and 20 parts of trimethylolpropane triacrylate was used. Prepare and apply this to UV-curable paint ()
shall be. This paint () was applied with a spinner onto an acrylic substrate on which Te was vapor-deposited, and cured by ultraviolet irradiation in the same manner as in Example 1 to form a protective film with a thickness of 10 μm. The hardness of the coating film was B on a pencil hardness scale. On top of this protective film, an ultraviolet curable paint () was further applied using a spinner, and then cured with ultraviolet irradiation to create a two-layer protective film with a thickness of 20 μm. The hardness of the upper protective film was H on a pencil hardness scale. This recording member also has excellent surface precision of the protective film, and no change in the recording medium Te was observed due to the application of the protective film, and He-N
The noise during laser reading is similarly small (S/N ratio 40dB), and the initial error rate is 2.8×10 ^-4
It was quite small. The writing sensitivity was even better than that of Example 1, and was possible at 6 mW and 500 nsec. This seems to be because a two-layer protective film was used, and the layer in contact with the recording medium Te was made a soft film. This recording member also had excellent moisture resistance as in Example 1 from the accelerated test results. Example 3 A paint was prepared in which epoxy acrylate was replaced with oleic acid-modified epoxy resin (composition ratio was the same) among the components of the ultraviolet curable paint in Example 1, and the results were recorded in the same manner and examined as a protective film for media. It was found to be a long-life protective film for optical recording media with excellent moisture resistance. Comparative Example 1 A butyl acetate solution of vinyl chloride-vinyl acetate copolymer (Denka Raku 31K, manufactured by Denki Kagaku Kogyo Co., Ltd.) was applied using a spinner onto an acrylic substrate on which Te was vapor-deposited.
After drying at room temperature, bake at 80℃ for 2 hours.
A recording member with a protective film having a thickness of 20 μm was prepared. Microscopic observation revealed that the surface precision of this protective film was inferior to that of Examples 1 and 2, and that a portion of the recording medium Te was degraded by the solvent. This seems to be because of this, but the noise when reading by shining a He-Ne laser through the protective film is due to the S/N ratio.
Even if the error rate is as high as 20dB before the acceleration test,
It was as high as 3.1×10 ^-3 . On the other hand, the deterioration of the recording member due to the accelerated test was also significant. Comparative Example 2 30 parts of polyester acrylate as a base resin of an ultraviolet curable paint, 20 parts of neopentyl glycol diacrylate as a reactive diluent,
A mixture of 10 parts of 2-ethylhexyl acrylate and 1.0 part of 2,2-diethoxyacetophenone as a photopolymerization initiator was prepared. The obtained UV-curable paint was applied onto a Te-deposited acrylic substrate and cured.
The thickness of the protective film of the obtained recording member was 20 μm. When the noise was examined in the same manner as in Example 1, it was found to be very small (S/N ratio approximately 40 dB), and the error rate before the acceleration test was also low. However, when an accelerated test similar to that in Example 1 was conducted, oxidation of the recording medium Te;
The blister phenomenon of the protective film was significant, and the error rate was also significantly increased. This is thought to be due to the high water content of the protective film and poor adhesion to the metal film of the recording medium. The results of the above Examples and Comparative Examples are summarized in the table below.

[Table] As described above, according to the present invention, by using a cured film made of an ultraviolet curable paint containing an epoxy resin modified with an unsaturated carboxylic acid as a base film as a protective film, it has excellent corrosion resistance and moisture resistance. An information recording member with a high S/N ratio, long life, and high sensitivity can be provided. In the present invention, the substrate on which the recording medium is attached is not limited to a disk shape, but may be a tape shape. Furthermore, the mode of writing information using laser light is not limited to forming recesses or holes in the recording medium according to the information, but may also utilize changes in refractive index or reflectance due to laser light irradiation. Furthermore, when recording is performed using recesses or holes, it is also possible to adopt a readout method that uses electrical capacitance changes in addition to information readout that uses laser light.

[Brief explanation of the drawing]

1 and 2 are views showing conventional information recording members, and FIGS. 3 and 4 are views showing information recording members according to embodiments of the present invention, respectively. DESCRIPTION OF SYMBOLS 11... Substrate, 12... Recording medium, 13... Protective film, 13 ₁ ... Soft film, 13 ₂ ... Hard film.

Claims (1)

[Claims] 1. In an information recording member that records information on a recording medium adhered to a predetermined substrate by irradiating laser light, a surface protective film of the recording medium may be modified with an unsaturated carboxylic acid. An information recording member characterized by using a cured film made of an ultraviolet curable paint containing an epoxy resin as a base. 2. The information recording member according to claim 1, wherein the unsaturated carboxylic acid is acrylic acid or methacrylic acid. 3. The information recording member according to claim 1, wherein the unsaturated carboxylic acid is a long chain unsaturated fatty acid having 5 or more carbon atoms. 4. The information recording member according to claim 1, wherein the protective film has a two-layer structure with a soft film as a base and a hard film laminated thereon.