JPH08124215A - Optical recording medium - Google Patents

Abstract

PURPOSE: To obtain an optical recording medium on the surface of which a character or a pattern can be formed well by laminating a light absorption layer, a light reflective layer, a protective layer containing an aromatic polyvinylacetal resin having specific mol.% of acetal extent, and a print layer sequentially on a transparent substrate. CONSTITUTION: An azo coloring matter is dissolved at 2.4wt.% into methyl Cellosolve and filtered and then a transparent polycarbonate substrate is spin coated with the solution to form a light absorption layer A. It is then dried in an oven at 0 deg.C to evaporate the solvent in the coloring matter layer and a gold film having average thickness of 100nm is sputtered on the layer A in Ar gas thus forming a light reflective layer B. The layer B is then coated with an UV-curing agent by 3μm which is eventually irradiated with UV-rays and cured to form a protective layer C. The protective layer C is coated with a solvent E which is then dried to form a print layer D. The solvent E is produced by dissolving a polyvinyl phenylacetoacetal resin having 2-40mol.% of extent of acetal into a 1:1 mixture solvent of water and isopropylalcohol. Consequently, a character or a pattern can be formed well on the layer D.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an optical recording medium. In particular, it relates to a protective layer or a printing layer of an optical information medium.

[0002]

2. Description of the Related Art An optical disc has a larger recording capacity than a conventional recording medium and can be randomly accessed.
It is widely used as a reproduction-only medium for audio software, computer software, game software, electronic publishing, and the like. On the other hand, write-once and rewritable recordable optical discs having an organic recording layer and an inorganic recording layer based on various recording principles have been developed and some of them have been put to practical use.

One of them is a recordable compact disc (CD-WO), which is capable of additional recording and has a reflectance equivalent to that of a read-only compact disc. It has the feature of being reproducible with. In recent years, this recordable compact disc has been widely distributed to individual users, and has come to be used for making a self-made CD by an amateur musician and making a self-made CD-ROM by a computer user. It is used for a number of other purposes to record personal information.

When recording personal information on an optical information medium, it is necessary to display an index of recorded contents and other designs on the surface of the disc. However, nothing is written on the outermost protective layer of recordable compact discs that have already been put to practical use / commercially available, or common characters and patterns are printed with UV curable ink or oil-based ink. Both the protective layer surface and the printed surface are hydrophobic. Therefore, the user cannot use a simple device such as an ink jet printer for printing the index or the like later, and it is difficult to print arbitrary information personally.

Therefore, in general, a method of writing on the surface of the protective layer or the printing layer using an oil-based felt pen or the like is adopted. However, there is a problem in that writing must be done by hand one by one, and in addition, variations in drawn patterns and drawing quality occur, and the appearance of the optical information medium is impaired. Further, depending on the type of resin used for the protective layer or the printing layer, the disk surface may not accept the oil-based ink. In that case, for example, a method of sticking a label or the like is adopted, but there is a problem that the display surface rises by the thickness of the label and causes eccentricity or surface wobbling of the optical information medium during reproduction or additional recording.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above conventional problems and provide an optical information medium capable of easily and satisfactorily forming a certain character or pattern on the surface of a protective layer or a printing layer. It is intended.

[0007]

As a result of intensive studies to solve the above problems, the present inventors achieved the above object by using a polyvinyl acetal resin in the protective layer or the printing layer. The inventors have found out that, and have reached the present invention. That is, the gist of the present invention is an optical recording medium in which at least a light absorbing layer and a light reflecting layer are sequentially laminated on a transparent substrate, and a protective layer or a printing layer is further laminated, in which the protective layer or the printing layer is made of a polyvinyl acetal resin. An optical recording medium characterized by including the above.

The optical recording medium of the present invention will be described in detail below. Examples of the transparent substrate used for the optical recording medium of the present invention include, but are not limited to, plastics such as polycarbonate, polymethylmethacrylate, and amorphous polyolefin, glass, and the like. A spiral guide groove or a tracking guide having another shape may be provided on the surface of such a transparent substrate.

As a material for forming the light absorption layer, an organic dye is preferably used, and examples thereof include a cyanine dye, a squarylium dye, a croconium dye, an azurenium dye, a triarylamine dye, an anthraquinone dye, and a dye. Metal azo dye, dithiol metal complex salt dye,
Indoaniline metal complex dye, phthalocyanine dye,
Naphthalocyanine dyes, intermolecular charge transfer dyes and the like are preferably used. These dyes may be used alone or in a mixture, and may be used in a form in which a deterioration inhibitor, a binder and the like are added if necessary.

As a method for forming the light absorbing layer containing such an organic dye, usually, a method of dissolving the organic dye or the like in an organic solvent and spin-coating on the transparent substrate is preferably used. The phthalocyanine dye A vapor deposition method can also be used for dyes having sublimability as described above. Further, as the light absorption layer, GeSeTe, which is an inorganic thin film,
Chalcogenide alloy thin film such as TeSe and TbFeC
It is also possible to use a rare earth-transition metal alloy thin film such as o.

The thickness of the light absorbing layer is usually 100Å to 5 μm.
m, preferably about 700 Å to 3 μm. The light-reflecting layer is usually formed of a material having a high reflectance with respect to the laser light used, and preferably a metal or alloy such as gold, silver, copper or aluminum is used. The light reflecting layer is usually formed by a sputtering method, a vacuum vapor deposition method, or the like, and is preferably a thin film having a film thickness of 50 to 200 nm.

If necessary, a dielectric layer, an organic polymer layer or the like may be provided between the substrate, the light absorption layer and the light reflection layer. When another layer such as a printing layer is provided on the protective layer, the protective layer is usually provided by applying a monomer and a polymer of an organic compound which can be polymerized into a polymer and then performing a crosslinking reaction. An ultraviolet curable resin is desirable as the material of the protective layer, but the material is not necessarily limited to this and may be a resin that crosslinks due to heat, moisture in the air, or other factors.
If necessary, additives such as a deterioration inhibitor, a diluent and a plasticizer may be contained. Further, it may be colored with a pigment or a dye. The material of the protective layer is not limited to organic compounds,
As the forming means, well-known means such as a sputtering method and a vapor deposition method other than coating can be applied. Such a protective layer may be composed of a plurality of layers made of different materials.

The optical recording medium of the present invention is characterized by containing a polyvinyl acetal resin as a material of the printing layer or the protective layer when another layer is not provided on the protective layer. The polyvinyl acetal resin exhibits various performances depending on the degree of acetalization and the type of acetal group. For example, in the case of a dry coating, the coating has oil resistance and water resistance, and has hydrophilicity even though it is not dissolved in water alone. Therefore, the polyvinyl acetal resin is water-based,
It has been found that both oil-based inks are suitable for the purpose of a protective layer or a printing layer having a good writing property. In particular, a polyvinyl acetal resin having an intermediate degree of acetalization or less or an aromatic polyvinyl acetal resin is preferable. Specifically, those having an acetalization degree of 2 to 40 mol% are preferable, and those having an acetalization degree of 5 to 20 mol% are particularly preferable. If the degree of acetalization is too low, the fixability of the ink is good, but the water resistance is poor, and if it is too high, the water resistance is good but the fixability of the ink is poor. Here, the degree of acetalization is A / (A + B + C) × 100 [mol%], where A is the number of moles of acetal groups contained in the polyvinyl acetal resin, B is the number of moles of acetyl groups, and C is the number of moles of hydroxyl groups. It is a numerical value represented by.

Such a printing layer or protective layer is usually
It is formed by applying a solution containing a polyvinyl acetal resin and drying it, but the forming method is not particularly limited. Further, various additives may be added to the printing layer or the protective layer depending on the purpose. For example, various pigments, pigment dispersants, surfactants, ultraviolet absorbers, wetting agents, defoaming agents, surface tension adjusting agents and the like may be added.

If necessary, an intermediate layer such as a second protective layer, an adhesive layer, a dye diffusion preventing layer and an elastic layer may be provided between the protective layer and the printing layer. Further, the ink receiving layer as in the present invention may be provided on the entire surface or a part thereof. The ink used in the optical information medium of the present invention is
Water-based or oil-based ink is preferable, but UV curable ink or the like may be used.

[0016]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist. Examples 1 to 10 As a transparent substrate, a recording groove having a meandering tracking groove for a compact recordable disk, having a diameter of 120 mm,
A polycarbonate substrate having a thickness of 1.2 mm was used.

The light absorbing layer was formed by dissolving the metal-containing azo dye in methyl cellosolve at a concentration of 2.4% by weight and filtering it, and then forming a film on the substrate by spin coating. After applying the dye, drying was performed in an oven at 80 ° C. for 10 minutes in order to completely evaporate the solvent in the dye layer. Next, a gold film having an average thickness of 100 nm is formed on the light absorption layer as a light reflection layer.
It was formed by a DC magnetron sputtering method in argon gas.

Further, on the light reflecting layer, an ultraviolet curing agent SD-
318 (manufactured by Dainippon Ink and Chemicals, Inc.) was applied by a spin coating method to a thickness of 3 μm and irradiated with ultraviolet rays by an ultraviolet ray irradiation device to be cured to form a protective layer. in addition,
A coating liquid prepared as described below was applied and dried to form a printing layer. In Example 1, 2 kg of water was added to 240 g of polyvinyl alcohol having a polymerization degree of 1600 and a saponification degree of 90.0 mol% and heated. When the polyvinyl alcohol was dissolved, the liquid was cooled, 120 g of 35 wt% hydrochloric acid and 50 g of phenylacetaldehyde were added, and the reaction was carried out at 10 ° C. for 5 hours. The degree of acetalization of the polyvinyl phenyl acetoacetal resin thus synthesized was 15 mol%. This resin was mixed with water: isopropyl alcohol = 1: 1.
It melt | dissolved in the mixed solvent of and was prepared.

In Examples 2 to 10 as well, in the same manner as in Example 1, several aldehyde species shown in Table 1 were used,
After synthesizing resins of each degree of acetalization, they were dissolved in the same mixed solvent as in Example 1 to prepare. When the printing layer was written with an oil-based felt pen, the oil-based ink dried in a few seconds in any of Examples 1 to 10 and showed very good fixability. In addition, a commercially available inkjet printer (FT Giken Co., Ltd., CD-
Printing was performed with the ROM printer FA949), and the fixing speed and water resistance of the printed image were measured.
The results shown in are obtained. The fixing time and water resistance evaluation methods and criteria in Table 1 are as follows. Fixing time The time until the ink is no longer transferred to the filter paper when the filter paper is pressed against the printing surface after ink ejection. The state of the ink image immediately after the printing surface was soaked in tap water for 1 minute and then pulled up after 1 hour from the jetting of the water resistant ink is shown as follows. ⊚: Same as before immersion. ◯: Swelled, but returns to the original state when the water is dried again. Δ: The ink partially elutes and the printing layer swells. X: The printed layer melts and flows away.

[0020]

[Table 1]

Comparative Examples 1 to 6 In Comparative Example 1, the degree of polymerization is 1600 and the degree of saponification is 90.
0 mol% of polyvinyl alcohol was applied onto a disc in which the same transparent substrate, light absorbing layer, light reflecting layer, and protective layer were sequentially laminated in the same manner as in Example 1 and dried to form a printing layer,
The same writing test and printing test as in Examples 1 to 10 were performed.

In Comparative Examples 2 to 6, printing layers were prepared in the same manner as in Example 1 except that the resins shown in Table 2 were used.
Its characteristics were evaluated. The results are shown in Table-2.

[0023]

[Table 2]

[0024]

INDUSTRIAL APPLICABILITY The present invention is industrially very useful because it can provide an optical information medium capable of easily and satisfactorily forming a certain character or pattern on the surface of the protective layer or the printing layer.

Claims (3)

[Claims] 1. An optical recording medium in which at least a light absorbing layer and a light reflecting layer are sequentially laminated on a transparent substrate, and a protective layer or a printing layer is further laminated, wherein the protective layer or the printing layer contains a polyvinyl acetal resin. Characteristic optical recording medium. 2. The optical recording medium according to claim 1, wherein the polyvinyl acetal resin is an aromatic polyvinyl acetal resin. 3. The optical recording medium according to claim 1, wherein the polyvinyl acetal resin has a degree of acetalization of 2 to 40 mol%.