JP2002237103A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium having a surface printable with a photograph-like image having high fineness and gloss. SOLUTION: The optical recording medium has an ink absorptive resin layer of >=30 to <=150 in 60 deg. mirror finished surface glossiness on the surface as the outermost layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium having a printable outermost layer. Note that “printable” means that writing with various writing tools and printing with various printers such as an ink jet printer and a thermal transfer printer are possible. In particular, the present invention can provide an optical recording medium having a printing characteristic of a full-color ink jet printer or a thermal transfer printer, more specifically, an aesthetic appearance excellent in gloss on a printed surface after printing as in a photograph.

[0002]

2. Description of the Related Art An optical recording medium (optical disk) on which information can be written and / or read by a laser has a larger recording capacity and random access than conventional recording media. It is widely used as a recording medium in fields such as computer software, game software, and electronic publishing.

[0003] Optical recording media are classified into two types: a write-once type, in which information can be recorded and reproduced, and a rewritable type, in which data can be erased after recording. In recent years, users of CD-R (write-once type) and CD-RW (rewriteable type) optical recording media of the CD system have been rapidly increasing in recent years. These CDs allow the user to write and use various information and data unique to each user, and the CD-R is compatible with the CD-ROM. Recently, DVD-R, a DVD-type optical recording medium,
(Write-once type), DVD-RW (rewritable type), etc. have also begun to spread.

It is preferable that a user of the optical recording medium as described above can understand at a glance what information is recorded on the medium. In addition, in the case of a company dealing with a small amount of various kinds of information media, such as putting the data in the medium and selling the medium to the end user, from the viewpoint of product labeling, writing performance with various writing tools on the medium surface, It is required to have printability with various printers.

In recent years, as the use of optical recording media has spread to general users, the purpose of designing the label surface of a disc is not only to discriminate the recorded contents, but also to enhance the artistry and to improve the quality of photographs. There is an increasing demand that data creators themselves want to design and freely design a desired pattern by printing and enjoying high-quality images. As a method of forming a design on the medium surface as described above, a method of directly attaching a paper or film label to the medium surface has been conventionally proposed, and a picture or a character designed according to one's preference can be freely printed on the medium surface. Although it has the advantage that it can be easily reproduced by an inexpensive personal printer, it also has the following disadvantages. (1) Due to the distribution of the weight of the label on the medium surface, rotation blur occurs, and errors in recording and reproduction signals are likely to occur during high-speed rotation. (2) The misalignment between the label and the medium is apt to occur, causing the problem of (1) due to lack of weight balance. In addition, if the label is unsuccessfully peeled off, the protective layer and the recording layer of the medium are removed. Is destroyed and the medium cannot be used. (3) If the label is peeled off or peeled off, the label may be caught in the drive device and destroy the disk or the drive. (4) The label expands and contracts due to moisture absorption and temperature change,
The medium is deformed, causing errors in recording and reproduction signals during high-speed rotation.

In order to solve such a drawback, an optical recording medium capable of directly printing on a surface (hereinafter referred to as a label surface) opposite to a recording / reproducing light incident surface of an optical recording medium, Printers have been released and their use is increasing. Many of such printers are of the aqueous liquid ink jet recording type, and many optical recording media having a water-absorbing label surface capable of accepting the ink of the ink jet printer have been sold. The outermost layer on the label surface that can receive (absorb) ink such as an ink jet printer is hereinafter referred to as a printable layer.

The components constituting the printable layer include:
For example, JP-A-7-169100 discloses that a printable protective layer (outermost layer) is formed from a UV-curable resin composition containing a hydrophilic polymer, a hydrophilic monomer, and a water-absorbing / oil-absorbing organic / inorganic filler. Optical recording media have been proposed. Japanese Patent Application Laid-Open No. 2000-5763 discloses a method for solving the problem of insufficient printability of the above system and enabling clear image formation in a printable layer of an optical recording medium.
Japanese Patent Application Laid-Open No. H05-205139 discloses prevention of bleeding and sharpness of an image formed on a printable layer, enhancement of water resistance of an image formed on the layer and the printable layer itself, and deterioration of recording characteristics of an optical recording medium. There has been proposed a printable layer which does not cause the problem and has good productivity.

In the configuration proposed in this publication,
Printing on the label surface of an optical recording medium with an ink-jet printer in the same way as printing on paper by absorbing and retaining the water that is the solvent of the ink of the ink-jet printer by the water-absorbing filler and hydrophilic resin. Is possible. Furthermore, due to the fine structure in the layer formed by the fine particles having an average particle diameter of 200 nm or less, the ink is absorbed without being diffused in the layer in the lateral direction, and the addition of the cationic resin causes the ink molecules in the ink jet printer to be printed in the printable layer. Thus, a clear image with little bleeding can be obtained by suppressing the diffusion and movement of the printed image, and a printable layer with little outflow of ink even when the printed image touches a water drop or the like.

[0009]

By using an optical recording medium having such a printable layer, even a general user can form an image such as a title, a number, and a picture on the label surface of the optical recording medium. This has made it possible to dramatically increase the degree of freedom in designing labels.

However, conventionally, in an optical recording medium having such a printable layer, if the surface is rough to make it easy to absorb the moisture of the ink, or if the portion where the image is printed absorbs the moisture of the ink, it is difficult to reflect light. As a result, the surface could not be made glossy, and only matte finishes could be made. On the other hand, with regard to printing paper dedicated to ink jet printers, high-grade products having a glossy surface are commercially available and widely accepted in order to obtain a printed image that is as close as possible to a photograph as the image quality is improved. This glossy paper has the effect of giving gloss and minimizing particles coming out on the outermost surface of the paper, thereby reducing the spread and bleeding of the ink, and making the printed image look clearer. .

Compared with the finish after printing on these specialty papers, the printable layer of the optical recording medium has a surface roughness (usually an arithmetic average roughness Ra of about 0.8 μm and a smoothness of 0.1 μm). About 6 μm), the size of the water-absorbing particles on the surface, and the lack of gloss (typically, a 60 ° specular gloss of about 20 or less) are inferior in printing performance and can be realized with paper. There is a problem that even a high definition design cannot be reproduced on the label surface of the optical recording medium.

[0012]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the outermost layer of the label surface of an optical recording medium can be formed as a layer having a small surface roughness, a gloss, and an ink absorbing performance. It has been possible to provide an optical recording medium having a glossy printable layer that allows a user to freely print a high-definition image having the same quality as a photograph on the medium surface with an ink jet printer or a thermal transfer printer. .

That is, the gist of the present invention is that the outermost layer
An optical recording medium characterized by having an ink-absorbing resin layer whose surface has a 60 ° specular gloss of 30 or more and 150 or less. In the present invention, the surface roughness (R
a) an optical recording medium characterized by having an ink-absorbing resin layer in which a) is 0.40 μm or less.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The optical recording medium of the present invention has (1) a surface 60 ° specular gloss of 30 to 150, and (2) surface roughness (Ra).
Is 0.40 μm or less, and (3) an ink absorbing resin layer as an outermost layer.

The effect of the present invention is remarkable when printing is performed on a label surface using an ink jet printer. However, the outermost layer of the optical recording medium of the present invention is compared with the print receiving layer of the conventional optical recording medium. Since the outermost layer surface is smooth, a beautiful label surface can be provided even when printing is performed with a thermal transfer printer. In addition,
Of course, it is also possible to fill out with ordinary writing tools instead of printing.

[0016] The 60 ° specular gloss is JIS K5400.
It is a value measured according to the description in 7.6. When the 60 ° specular gloss is less than 30, the gloss of the outermost layer surface of the optical recording medium is insufficient, so that a clear and glossy image cannot be obtained after inkjet printing. Also 150
When the value exceeds, the reflection component from the outermost layer of the optical recording medium becomes extremely large, and it is difficult to continuously view the image printed on the outermost layer for a long time, which is not preferable. Further, there is a problem that the manufacturing cost is increased. More preferably, the 60 ° specular gloss is 50 to 120.

The surface roughness can be measured using a commercially available surface roughness meter. If the surface roughness exceeds 0.40 μm, the diffuse reflection component from the outermost layer surface becomes large, and the haze (cloudiness) value becomes large, which may cause a problem that the printed image becomes apparently unclear. The surface roughness (Ra) is more preferably 0.30 μm or less.

The optical recording medium of the present invention must satisfy either (1) or (2), but (1)
It is more preferable that the above conditions are satisfied. The glossy printable layer which is the outermost layer in the optical recording medium of the present invention has ink absorbability. The ink may be a water-based ink or an organic solvent-based ink as used in an ink-jet ink, and the gloss printable layer of the present invention is preferably one that can absorb any of an organic solvent-based or water-based ink. In the case of inkjet recording, which is a general-purpose printing method, a water-based ink using water as a solvent is generally used.

Next, the composition and method of forming the glossy printable layer as the outermost layer will be described. In general, as a means for forming a print receiving layer on paper or a film, a method is known in which a composition containing a resin soluble in water or another solvent as a binder is applied and dried. In this case, of course, the water resistance and solvent resistance of the print receiving layer itself are weak.
In addition, the drying time requires a minimum of several minutes, which is not preferable in terms of productivity in the process of manufacturing an optical recording medium. Further, the characteristics of the medium may be deteriorated by the influence of the drying heat. On the other hand, in the present invention, for example, ultraviolet (UV)
By using a resin composition (ultraviolet curable resin composition) having a curable resin as a binder as a raw material of a printable layer (print receiving layer) of an optical recording medium, the layer itself has high water resistance and high solvent resistance. Layers can be formed.

In general, ultraviolet curable resins are classified into radical reaction type resins and ion reaction type resins. In general, ion reaction type resins have a slow reaction rate, and thus radical reaction type resins are preferably used. . The radical reaction type UV curable resin is usually prepared by using at least a resin monomer component and a photopolymerization initiator, and further using a resin oligomer component as necessary. By variously selecting the resin monomer component and the resin oligomer component, it is possible to obtain a print receiving layer having various characteristics according to the liquid properties of the ink used. That is, the viscosity and hardness change depending on the type and amount of the resin monomer component, and the hardness, adhesion, water resistance, moisture resistance, and the like change depending on the type and amount of the resin oligomer component. In the present invention, the oligomer refers to a polymer having a molecular weight of about 8000 or less.

The resin monomer component may be a monofunctional or polyfunctional monomer, but preferably contains a certain amount of a polyfunctional monomer component in order to increase the crosslink density in the printable layer and maintain strength. As the monofunctional monomer, for example, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, phenoxyethyl acrylate, nonylphenoxyethyl acrylate, N-vinylpyrrolidone, 2-hydroxyethylacryloyl phosphate, tetrahydrofurfuryl acrylate , Tetrahydrofurfuryloxyethyl acrylate, tetrahydrofurfuryloxyhexanolide acrylate, 1,
An acrylate of an ε-caprolactone adduct of 3-dioxane alcohol, 1,3-dioxolan acrylate, and the like are included.

Examples of polyfunctional monomer components include cyclopentenyl acrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, tripropylene glycol diacrylate, neopentyl glycol diacrylate, polyethylene glycol (400) diacrylate, and hydroxypivalin. Acid ester neopentyl glycol diacrylate, diacrylate of neopentyl glycol adipate, diacrylate of ε-caprolactone adduct of neopentyl glycol hydroxypivalate, 2- (2-hydroxy-
1,1-dimethylethyl) -5-hydroxymethyl-5
-Ethyl-1,3-dioxane diacrylate, tricyclodecane dimethylol diacrylate, diacrylate of ε-caprolactone adduct of tricyclodecane dimethylol, trimethylolpropane triacrylate,
Pentaerythritol triacrylate, dipentaerythritol hexaacrylate, propionic acid / dipentaerythritol triacrylate, hydroxypivalaldehyde-modified dimethylolpropane triacrylate, propionic acid / dipentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, etc. .

Examples of the resin oligomer component include acrylic oligomer, ester oligomer, urethane oligomer, ether oligomer and the like. These may be used alone, but when used in combination of two or more, a print receiving layer having different characteristics is obtained.
For example, when an ester oligomer is used together with an acrylic oligomer, a water-resistant and hard layer can be obtained. In this case, since the curing shrinkage is large, the medium may be warped, but this can be solved by giving the substrate a warp in the opposite direction in advance. On the other hand, when a urethane oligomer is used together with an acrylic oligomer,
Since the urethane-based oligomer has a large molecular weight and small curing shrinkage, the possibility that the substrate is warped or the like is reduced. In this case, the formed cured coating film is relatively soft.

Examples of the above acrylic oligomer include (meth) acrylic acid, and alkyl such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and butyl (meth) acrylate. A polymer of (meth) acrylate or the above monomer,
Aromatic vinyl compounds such as styrene, α-methylstyrene, (o, m, p) vinylphenol, vinyl carboxylic acid compounds such as maleic acid, itaconic acid, crotonic acid and fumaric acid, glycidyl (meth) acrylate, allyl glycidyl ether Glycidyl group-containing vinyl compounds such as glycidyl ethyl acrylate, crotonyl glycidyl ether, glycidyl crotonate, aromatic acrylate compounds such as benzyl (meth) acrylate, hydroxyethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) A) a substituted alkyl acrylate compound such as acrylate, (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylamide, etc. Riruamido compounds, vinyl acetate,
A copolymer with a compound selected from (meth) acrylonitrile, (meth) acrylic acid chloride, N- (meth) acryloylmorpholine and the like can be mentioned.

Examples of the ester oligomer include, for example, an ester of acrylic acid and a polyester diol composed of a ring-opening polymer of phthalic anhydride and propylene oxide, and a polyester diol composed of adipic acid and 1,6-hexanediol and an acrylic acid. Esters with an acid, esters of a triol with a reaction product of trimellitic acid and diethylene glycol with an acrylic acid, esters of a ring-opening polymer of δ-valerolactone with an acrylic acid, and the like.

Examples of the urethane oligomer include a reaction product of polyurethane composed of hexamethylene diisocyanate and 1,6-hexanediol with 2-hydroxyethyl acrylate, and a polyester diol composed of adipic acid and 1,6-hexanediol. And 2-hydroxyethyl acrylate reacted with a diisocyanate oligomer obtained by reacting a polyisocyanate with tolylene diisocyanate.

Examples of the ether-based oligomer include esters of polypropylene glycol and acrylic acid. In addition, epoxy oligomers, polyarylates, and the like obtained by reacting an acrylate with an epoxy resin can also be used as the resin oligomer component. As the photopolymerization initiator, for example, benzoin isopropyl ether, benzophenone, 2-hydroxy-2
-Methylpropiophenone, 1-hydroxycyclohexylphenyl ketone, 2,4-diethylthioxanthone, methyl o-henzoylbenzoate, 4,4-bisdiethylaminobenzophenone, 2,2-diethoxyacetophene, benzyl, 2-chlorothioxanthone , Diisopropylthiozanson, 9,10-anthraquinone, bensoin, bensoin methyl ether, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-
2-methyl-propiophenone, 4-isopropyl-2
-Hydroxy-2-methylpropiophenone, α, α-
Dimethoxy-α-phenylacetone and the like.

The content of each component in the ultraviolet curable resin composition for forming a glossy printable layer, which is the outermost layer in the optical recording medium of the present invention, is usually 0.1% for the photopolymerization initiator.
1 to 20% by weight, 50 to 90% by weight of monomer, and 0 to 30% by weight of oligomer. If the amount of the oligomer is too large, the composition tends to thicken, and application may be difficult.

When the ultraviolet curable resin composition is used for forming a gloss printable layer, for example, an ink solvent (generally water) must be absorbed when an ink jet printer is used. It is desirable to include a filler. In particular, since the composition is used for forming a high-gloss layer, it is desirable that the composition does not deteriorate the surface roughness of the coating film and does not scatter light much, and the composition does not give much color.

Examples of such a water-absorbing filler include various fine particles of organic and inorganic substances. For example, as fine particles composed of organic substances, synthetic resin particles such as PMMA resin, polystyrene resin, epoxy resin, fluororesin, silicone resin, polyester resin, collagen, silk,
Natural resin particles such as cotton. Examples of the inorganic fine particles include oxides of various metals such as aluminum, magnesium, zinc, iron, manganese, and titanium, as well as talc and mica, and ceramics. Among inorganic fine particles, porous ones show particularly good characteristics,
Examples include porous synthetic amorphous silica, porous alumina, porous magnesium carbonate, and the like.

[0031] Synthetic silica is recommended because the particle size and specific surface area can be controlled by the production method, and spherical fine particles having uniform characteristics can be obtained. There are a dry method and a wet method as a method for synthesizing the synthetic silica, and a wet method is preferable to obtain porous silica having a large specific surface area. Further, the wet method includes a precipitation method and a gel method, and any of them may be used. The average particle diameter of these particles is preferably 1 μm or less, more preferably 300 nm or less, so as not to deteriorate the surface roughness of the outermost surface of the optical recording medium.

The amount of the filler in the printable layer of the present invention is 15 parts by weight based on 100 parts by weight of the total of the photopolymerization initiator, monomer and oligomer contained in the ultraviolet-curable resin composition forming the gloss printable layer. It is not less than 100 parts by weight, preferably not less than 15 parts by weight and not more than 60 parts by weight, more preferably not less than 15 parts by weight and not more than 50 parts by weight. If the amount is less than 15 parts by weight, the effect of absorbing the moisture of the ink is inferior, and the surface of the gloss printable layer becomes sticky or a good image cannot be obtained after printing.

The UV-curable resin composition may further comprise a polymerization terminator, a storage stabilizer, a dispersant, a defoaming agent,
A binder resin other than the ultraviolet curable resin may be contained. Gloss printable layer in the present invention, according to a conventional method, for example, spin-coating method, dip coating method, bar coating method, blade coating method, air knife coating method, roll coating method, the above-mentioned ultraviolet curable by a method such as screen printing method It is obtained by irradiating ultraviolet rays after applying the resin composition.

By the way, since UV-curable screen printing machines are usually used for printing on the label surface of an optical disc or the like, these printing machines are also used and formed by screen printing. The device and the process time of the layer forming process are greatly improved. In addition, in the case of using a spin coating method, the viscosity of the ultraviolet curable resin composition is desirably 40 P or less in that a uniform coating film having a surface roughness Ra of 0.4 μm or less is obtained, and a screen printing method is used. In that case, 40-100
It is desirable to be in the range of P.

A high-pressure mercury lamp, a metal halide lamp or the like is used as a light source for ultraviolet irradiation used for curing the composition. The irradiation energy amount is usually 150 to 20.
00 mJ / cm ² , preferably 250-1000 mJ /
selected from the range of cm ² . At this time, since the coating film is cured in a few seconds, the productivity is excellent. However, when a screen printing method is used as a method for forming a coating film, a leveling agent is added for the purpose of smoothing the coating film surface and releasing bubbles from the coating film instantly to increase the glossiness of the coating film surface. Is preferred. As the leveling agent, silicone oil or the like is preferable.

The gloss printable layer of the present invention can be prepared by, for example, making the viscosity of the composition for forming a layer relatively small, devising a leveling agent to be blended, reducing the particle size of the filler,
In the case of forming by a screen printing method, it can be achieved by various means or a combination thereof such as optimizing a screen mesh (for example, to about # 300 to # 400). The optical recording medium of the present invention may have an underlayer formed using an ultraviolet-curable resin composition in contact with the resin layer as the outermost layer or through another layer. Preferably, the underlayer is opaque, is ink-absorbing like the outermost layer, or both.
The underlayer is preferably formed using an ultraviolet-curable resin composition for the same reason as the outermost layer, and the components of the composition are the same as those described above in the description of the outermost layer. Can be used. When the underlayer is simply an opaque ultraviolet-curable resin layer, it is not necessary to absorb the ink, so that the liquid absorbing property (water absorbing property)
The filler may not be contained.

It is preferable to use an opaque underlayer so that the printed image can be seen more clearly. In particular, it is preferable to provide a white or near-white light-colored underlayer because the printed image has high color purity and looks sharp. By forming the underlayer as an ink-absorbing layer formed using a UV-curable resin composition, the ink penetrating from the outermost layer is absorbed by the underlayer, and the drying property and water resistance of the image are improved. It is preferable because it can be increased.

In the case of forming an ink-absorbing underlayer, the same raw material as that of the outermost layer can be used. However, since the underlayer does not need to exhibit gloss, the ink absorbing property can be further improved. With an excellent structure, the ink absorbed by the outermost layer can be further penetrated into the inside, so that the drying property and water resistance of the image can be further improved. The water-absorbing filler particles may have a roughness of 1 μm to 20
Particles having a particle size of about μm or less can also be used.

In any of these cases, when an epoxy-based oligomer or a urethane-based oligomer is used as the base resin of the ultraviolet-curable resin composition, coloring can be freely performed and curing shrinkage is small. It is desirable that the mechanical properties of the completed optical recording medium be good. The same additives as in the outermost layer can be used.

For formation of the underlayer, offset printing, pad printing, screen printing and the like can be used. In particular, screen printing is realized because a large-scale apparatus with excellent productivity is realized. If such an apparatus is used, it can be formed at the same time as the outermost printable layer. Next, other layers, layer configurations, and the like that constitute the optical recording medium of the present invention will be described.

The optical recording medium of the present invention is preferably formed by laminating at least a recording layer, a light reflecting layer and an outermost gloss printable layer on a transparent substrate. Further, a protective layer may be provided between the outermost gloss printable layer and the reflective layer, or between the base layer and the reflective layer. Note that the outermost layer may cover the entire label surface of the optical recording medium, or may partially cover it.

The kind of the resin for the protective layer is not particularly limited, but is preferably an ultraviolet curable resin as in the case of the outermost gloss printable layer. Specifically, the same monomers, oligomers, and photopolymerization initiators as those exemplified above as usable for the gloss printable layer can be used, and if necessary, a polymerization terminator, a storage stabilizer, and the like. The same applies to the point that an antifoaming agent, a binder resin and the like can be used. However, since the protective layer does not need to have ink absorbability, it does not need to include components necessary for imparting absorbability, such as a filler and a dispersant.

As the layer forming method (coating method), the same method as that for the gloss printable layer can be used, and among them, the spin coating method is most common. The protective layer may have two or more layers as necessary. As a transparent substrate, for example,
In addition to polymer materials such as polycarbonate resin, acrylic resin, polystyrene resin, vinyl chloride resin, epoxy resin, polyester resin, and amorphous polyolefin,
An inorganic material such as glass is used. In particular, a polycarbonate-based resin is preferable because of its high light transmittance and small optical anisotropy.

On the surface of the transparent substrate, guide grooves, pits and the like (groove information, etc.) representing recording positions are usually formed. The groove information or the like is usually given when a substrate is made by injection molding or casting, but may be made by a laser cutting method or a 2P method (Photo-Polymer method). The recording layer is not particularly limited as long as it can be recorded by laser light irradiation, and may be either a recording layer made of an inorganic substance or a recording layer made of an organic substance.

In the recording layer made of an inorganic substance, for example, Tb-Fe-Co or Dy-F for performing recording by the photothermal magnetic effect is used.
A rare earth transition metal alloy such as e.Co is used. Also,
Chalcogen-based alloys such as Ge.Te and Ge.Sb.Te that change phases may also be used. In the recording layer made of organic substances,
Mainly, organic dyes are used. Such organic dyes include macrocyclic azaannulene dyes (phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, etc.),
Polymethine dyes (cyanine dyes, merocyanine dyes,
And anthraquinone dyes, azurenium dyes, metal-containing azo dyes, metal-containing indoaniline dyes, and the like. In particular, metal-containing azo dyes are preferable because of their excellent durability and light resistance.

The dye-containing recording layer can be formed by, for example, an evaporation method or a coating method, but is usually formed by a coating method such as spin coating, spray coating, dip coating, or roll coating. In this case, the solvent may be a ketone alcohol solvent such as diacetone alcohol or 3-hydroxy-3-methyl-2-butanone, a cellosolve solvent such as methyl cellosolve or ethyl cellosolve, or a perfluoro solvent such as tetrofluoropropanol or octafluoropentanol. Alkyl alcohol solvents, hydroxyethyl solvents such as methyl lactate and methyl isobutyrate are preferably used.

The light reflecting layer is usually made of gold, silver, aluminum, or an alloy thereof, but when an organic dye is used for the recording layer, it is particularly preferable to be made of silver or a silver alloy. The metal reflection layer is formed by a vapor deposition method, a sputtering method, or an ion plating method. Note that an intermediate layer may be provided between the metal reflective layer and the recording layer for the purpose of improving the adhesion between the layers or for the purpose of increasing the reflectance.

The thickness of the above recording layer is usually 10 to 5000
nm, and the thickness of the light reflecting layer is usually 50 to 200 nm.
The thickness of the outermost gloss printable layer is usually 5 to 50μ.
m, preferably 10 to 25 μm, and the thickness of the underlayer is usually 5
５０50 μm, preferably 5-25 μm, and the total thickness of the gloss printable layer and the underlayer is preferably 10
It is 70 μm, more preferably 15 to 30 μm. The thickness of the underlayer is usually about 1/3 to 2 times the thickness of the gloss printable layer. The thickness of the protective layer is usually 1 to 10 μm.

When the thickness of the gloss printable layer is less than 5 μm, it is difficult to secure the volume of the water-absorbing filler necessary for absorbing the ink, and the unabsorbable ink remains on the surface of the printable layer, thereby causing image blurring. May cause. On the other hand, when the thickness exceeds 50 μm, the absorption and penetration of the ink proceeds to the inside of the layer, and the color developability of the ink on the surface of the printable layer is reduced, and the sharpness of the image may be reduced. In addition, as described above, the shrinkage stress of the ultraviolet curable resin increases, and the possibility that an optical recording medium is warped to cause an error when recording and reproducing information increases. Further, the ultraviolet ray transmission is poor at the time of ultraviolet ray irradiation, and there is a possibility that the inside of the layer may be insufficiently cured.

The optical recording medium of the present invention may have a structure in which a recording layer, a reflective layer, a protective layer, a printable layer, and the like are sequentially laminated on a substrate as described above. A structure in which a substrate necessary for optical recording such as a layer is laminated and a substrate is further laminated (laminated) may be used. In this case, the surface (outermost layer) of the substrate which is laminated later is coated on the surface (outermost layer) of the present invention. What is necessary is just to form a gloss printable layer and an underlayer.

[0051]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention. Example 1 A solution of a metal-containing azo dye was dropped on an injection-molded polycarbonate resin substrate (120 mm in diameter) having a depth of 1600 mm and a width of 0.45 μm and having a groove, and was rotated at 500 rpm by spin coating. Apply, 90
It dried at 30 degreeC for 30 minutes, and formed the recording layer.

Next, a silver film having a thickness of 800 ° (80 nm) was formed on the recording layer by sputtering to form a reflective layer. Then, a transparent ultraviolet curable resin was spin-coated on the entire surface of the reflective layer, and then cured by irradiating ultraviolet rays to form a 5 μm protective layer. Furthermore,
An ultraviolet curable resin composition having the composition shown in Table 1 was applied to the entire surface of the protective layer by screen printing, and then cured by irradiating ultraviolet rays to form a gloss printable layer having a thickness of 20 μm.

[0053]

[Table 1]

Example 2 After forming the protective layer and before forming the outermost layer, an ultraviolet-curable resin composition having the composition shown in Table 2 was applied to the entire surface of the protective layer by screen printing, and then irradiated with ultraviolet rays. An optical recording medium was prepared in the same manner as in Example 1, except that the resin was cured to form an opaque ultraviolet curable resin layer (underlayer) having a thickness of 20 μm.

[0055]

[Table 2]

Example 3 After forming the protective layer and before forming the outermost layer, an ultraviolet-curable resin composition having the composition shown in Table 3 was applied to the entire surface of the protective layer by screen printing, and then irradiated with ultraviolet rays. An optical recording medium was prepared in the same manner as in Example 1, except that the resin was cured to form a water-absorbing ultraviolet-curable resin layer (underlayer) having a thickness of 20 μm.

[0057]

[Table 3]

Example 4 As in Example 1, after forming up to the protective layer on the substrate and before forming the outermost layer, the entire surface of the protective layer was screened with an ultraviolet curable resin composition having the composition shown in Table 3. After being applied by printing, it is cured by irradiating ultraviolet rays, and has a water-absorbing UV-curable resin layer (underlayer) having a thickness of 20 μm.
Was formed. An ultraviolet curable resin composition having the composition shown in Table 1 was applied on the underlayer by spin coating, and was cured by irradiating ultraviolet rays to form an outermost gloss printable layer having a thickness of 6 μm.

The spin-coating conditions were as follows: about 10 ml of the ultraviolet-curable resin composition shown in Table 1 was dropped on the inner periphery of the label surface of the optical recording medium, rotated at 200 rpm and spread over the entire surface.
The outermost glossy printable layer was formed by shaking off with the rotation speed increased to rpm. The optical recording medium obtained above had a 60-degree specular glossiness of 70 and a surface roughness of R
a was 0.15 μm. Comparative Example 1 An optical recording medium was prepared in the same manner as in Example 1 except that the outermost layer was formed using an ultraviolet curable resin composition having the composition shown in Table 3 instead of the composition shown in Table 1. did. [Evaluation] The 60 ° specular gloss of the outermost layer surface of the optical recording medium prepared in each of Examples and Comparative Examples was measured according to JIS K54.
It was measured with a cardner gross meter according to 00.
The surface roughness (Ra) was measured using a surface roughness meter Mitutoyo Surf Tester 402. Table 4 shows the results.

[0060]

[Table 4]

Next, a photographic image was printed on the outermost layer of the optical recording medium obtained in each of Examples and Comparative Examples using an ink jet printer “PM-900C” manufactured by Epson Corporation.
In Examples 1 to 3 and Comparative Example 1, clear images without bleeding or spreading were obtained. However, in Examples 1 to 3, the image had a high-grade appearance due to the surface gloss not seen in Comparative Example 1, and could not be expressed by the conventional inkjet printing on the label surface of the optical recording medium. It had the texture of a silver halide photograph. Above all, the optical recording medium obtained in Example 4 provided a particularly beautiful image.

As described above, in the optical recording medium of the present invention, characters and pictures were printed on the label surface by an ink jet printer or the like by providing a glossy printable layer having a gloss and a small surface roughness as the outermost layer as compared with the conventional product. In this case, the label surface of the optical recording medium having a feeling of high quality and having a texture for silver halide photography was obtained as compared with the case of the single layer of the printable layer having no gloss.

[0063]

As described above, according to the present invention, an optical recording medium which can be printed on a label surface by an ink jet printer or a thermal transfer printer, has a glossy surface, and gives a printed image a sense of quality. In addition, it is possible to provide a label surface of an optical recording medium having a texture similar to silver halide photography.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G11B 11/105 526 B41M 5/26 H (72) Inventor Yuji Kawamura 1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa-ken Mitsubishi Chemical Corporation EA04 FB01 FC06 2H086 BA01 BA15 BA19 BA33 BA36 BA41 BA44 2H111 AA01 AA05 CA03 CA14 CA25 CA30 CA33 CA41 5D029 PA01 5D075 FH10

Claims (8)

[Claims] 1. An optical recording medium comprising, as an outermost layer, an ink-absorbing resin layer whose surface has a 60 ° specular gloss of 30 to 150. 2. An outermost layer having a surface roughness (Ra) of 0.5.
An optical recording medium having an ink-absorbing resin layer having a thickness of 40 μm or less. 3. The optical recording medium according to claim 2, wherein the outermost resin layer has a 60 ° specular gloss of 30 to 150 on the surface. 4. The optical recording medium according to claim 1, wherein the outermost layer is formed using an ultraviolet curable resin composition. 5. The optical recording medium according to claim 1, wherein the outermost layer contains porous alumina fine particles or porous silica fine particles. 6. An opaque underlayer formed by using an ultraviolet-curable resin composition in contact with a resin layer which is an outermost layer or through another layer. 3. The optical recording medium according to claim 1. 7. An ink-absorbing base layer formed by using an ultraviolet-curable resin composition in contact with a resin layer as an outermost layer or through another layer.
The optical recording medium according to any one of the above. 8. The optical recording medium according to claim 7, wherein the underlayer is an opaque layer.