Optical recording medium

[0001] [Technical field to which the invention belongs] The present invention relates to an optical recording medium, and in detail,<u style="single">By inkjet printer</u>The present invention relates to an optical recording medium having a surface layer (print receiving layer) capable of printing. [0002] [Conventional technology] Optical recording media (optical discs) that can write and / or read information by laser have a larger recording capacity and can be accessed randomly than conventional recording media. Therefore, audio software, computer software, and game software. , Widely used as a recording medium in fields such as 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. Among them, the number of users of CD-R (additional type) and CD-RW (rewrite type), which are CD-type optical information media, has been increasing rapidly in recent years. Each of these CDs can be used by each user by writing various information and data unique to the user, and the CD-R is compatible with a read-only CD. Recently, DVD-R (write-once type), DVD-RW (rewrite type), and the like, which are DVD-type optical recording media, have begun to spread. [0004] For users of the optical recording medium as described above, it is preferable to make it possible to see at a glance what kind of information is recorded on the medium. In addition, in the case of a trader who handles a wide variety of small-lot information media, such as putting data in a medium and selling the medium to end users, from the viewpoint of product labeling, the surface of the medium should be printable by various printers. It is required to have. [0005] For the above reasons, in recent years, the opposite of the light incident surface of the optical recording medium<u style="single">On the side</u>Outermost<u style="single">Layer</u>Optical recording media formed by a print receiving layer and capable of direct printing and printers dedicated to such media have come to be sold. Water-based liquid inkjet recording methods and heat-sensitive transfer methods are often used as printing recording methods for these printers. These recording methods are widely used because they are relatively inexpensive and can obtain clear full-color images. [0006] By the way, due to a design or trademark request, a manufacturer of an optical recording medium may also print on a print receiving layer. However, for example, when printing by a manufacturer of an optical recording medium is performed with ordinary printing ink, the printed surface cannot be overprinted later by a user or the like. [0007] [Problems to be Solved by the Invention] The present invention has been made in view of the above circumstances, and an object of the present invention is that even though characters and patterns are drawn on the print receiving layer by a manufacturer of an optical recording medium, subsequent printing by a user or the like is completely performed. It is an object of the present invention to provide an improved optical recording medium so that it can be performed without any trouble. [0008] [Means for solving problems] That is, the gist of the present invention is formed by a print receiving layer for an inkjet printer in which the outermost layer on the surface opposite to the light incident surface is composed of an ultraviolet curable resin composition containing fine particles having an average particle size of 200 nm or less and a cationic resin. ,<u style="single">Forming surface of the outermost layer</u>Is present in an optical recording medium characterized in that is divided into a plurality of regions having different colors. Here, "different colors" means that the hue, lightness, saturation, luster, texture, and the like are different to the extent that they can be visually discriminated. [0009] 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 at least a recording layer, a light reflecting layer, and a transparent substrate on a transparent substrate.<u style="single">For inkjet printers</u>The print receiving layer is sequentially laminated. Here, the print receiving layer is the outermost layer on the surface opposite to the light incident surface. [0010] As the transparent substrate, for example, polymer materials such as polycarbonate resin, acrylic resin, polystyrene resin, vinyl chloride resin, epoxy resin, polyester resin, and amorphous polyolefin, as well as inorganic materials such as glass are used. In particular, a polycarbonate resin is preferable because it has high light transmission and low optical anisotropy. [0011] A guide groove, a pit, or the like (groove information or the like) indicating a recording position is usually formed on the surface of a transparent substrate. Groove information is usually given when a substrate is made by injection molding or casting, but it may be made by a laser cutting method or a 2P method (Photo-Polymer method). [0012] The recording layer is not particularly limited as long as it can be recorded by irradiation with laser light, and may be either a recording layer made of an inorganic substance or a recording layer made of an organic substance. [0013] For the recording layer made of an inorganic substance, for example, a rare earth transition metal alloy such as Tb / Fe / Co or Dy / Fe / Co that records by the photothermal magnetic effect is used. In addition, chalcogen-based alloys such as Ge / Te and Ge / Sb / Te that change phase can also be used. [0014] An organic dye is mainly used for the recording layer made of an organic substance. Such organic pigments include macrocyclic azaanulene pigments (phthalocyanine pigments, naphthalocyanine pigments, porphyrin pigments, etc.), polymethine pigments (cyanine pigments, merocyanine pigments, stawarylium pigments, etc.), anthraquinone pigments, azulenium pigments, and metal-containing pigments. Examples include azo dyes and metal-containing Indian aniline dyes. In particular, metal-containing azo dyes are preferable because they are excellent in durability and light resistance. [0015] The dye-containing recording layer is usually formed by a coating method such as spin coating, spray coating, dip coating, or roll coating. At this time, as the solvent, a ketone alcohol solvent such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone, a cellosolve solvent such as methyl cellosolve and ethyl cellosolve, and perfluoro such as tetrofluoropropanol and octafluoropentanol are used. A hydroxyethyl solvent such as an alkyl alcohol solvent, methyl lactate, and methyl isobutyrate is preferably used. [0016] The light reflecting layer is usually composed of gold, silver, aluminum or the like, but when an organic dye is used for the recording layer, it is particularly preferable to be composed of silver. The metal reflective layer is formed by a vapor deposition method, a sputtering method, or an ion plating method. An intermediate layer may be provided between the metal reflective layer and the recording layer in order to improve the adhesion between the layers or for the purpose of increasing the reflectance. [0017] The thickness of the recording layer is usually 10 to 5000 nm, the thickness of the light reflecting layer is usually 50 to 200 nm, the thickness of the print receiving layer is usually 5 to 50 μm, and the thickness of the protective layer is usually 1 to 10 μm. [0018] In the optical recording medium of the present invention, the outermost layer on the surface opposite to the light incident surface is formed of a print receiving layer for an inkjet printer.<u style="single">Forming surface of the outermost layer</u>Is characterized in that it is divided into multiple areas with different colors. That is, in the optical recording medium of the present invention, as a result of some printing on the above-mentioned print receiving layer by the manufacturer of the optical recording medium due to a design or trademark request, the user or the like superimposes on the optical recording medium. The problem of being unable to print is solved at once. [0019] Then, when considering overprinting by the user, it is preferable that the color of the print receiving layer itself is light. Specifically, it is preferable that the XYZ color system chromaticity coordinates (x, y) of the reflected light in an arbitrary region of the print receiving layer satisfy the following equation (1a), preferably (1b). [0020] [Number 3]<img file="JP4530474B2_D0001.tif" />[0021] [0021] Further, when the contrast of each region of the print receiving layer is large, the printing performed by the manufacturer stands out, but the overlay printing by the later user may be unclear, so that the regions may have similar colors. preferable. Specifically, the XYZ color system chromaticity coordinates (x) of the reflected light at any two points on the print receiving layer.₁, y₁) And (x₂, y₂) Satisfies the following equation (2a), preferably (2b). [0022] [Number 4]<img file="JP4530474B2_D0002.tif" />[0023] For overprinting by users<u style="single">, Cheap</u>Inkjet method because of its high price and high printing speed<u style="single">Is adopted.</u>[0024] As a material for the print receiving layer<u style="single">, Fu</u>With a print receiving layer that has excellent print characteristics, storage stability, and print water resistance of a Lucolor liquid inkjet printer.<u style="single">To do</u>, The print receiving layer described in JP-A-2000-57635 proposed by the present applicant, that is, an ultraviolet curable resin composition containing fine particles having an average particle size of 200 nm or less and a cationic resin.<u style="single">To use.</u>[0025] As described above, by containing a predetermined amount of fine particles in the print receiving layer, it is possible to form fine voids in the print receiving layer so that the ink is instantly absorbed by the capillary phenomenon. According to this method, since a large amount of ink can be absorbed, the spread (bleeding) of the ink on the surface of the print receiving layer can be controlled, and the absorption rate can be increased, so that the drying property is improved and a clear image is obtained. Can be formed. [0026] Examples of the above-mentioned fine particles include various fine particles of organic and inorganic substances. For example, examples of fine particles composed of organic substances include synthetic resin particles such as PMMA resin, polystyrene resin, epoxy resin, fluororesin, silicon resin, and polyester resin, and natural resin particles such as collagen, silk, and cotton. Examples of fine particles composed of inorganic substances include oxides of various metals such as aluminum, magnesium, zinc, iron, manganese, and titanium, ceramics, and the like, in addition to talc and mica. Fine particles made of organic substances are preferable because it is difficult to make them into fine particles having a particle size of 100 nm or less, and they tend to be inferior in heat resistance, water resistance, solvent resistance, and the like. Among the inorganic fine particles, various metal oxides are preferable because they can be easily atomized. In particular, silica is suitable because it has a large specific surface area, can form fine voids, and has a hydrophilic surface, so that it has good compatibility with water-based inks. [0027] Synthetic silica is recommended because the particle size, specific surface area, etc. can be controlled by the production method, and fine particles having spherical and uniform characteristics can be obtained. There are two methods for synthesizing synthetic silica, a dry method and a wet method. In order to obtain silica having a large porous surface area, the wet method is preferable. Further, the wet method includes a precipitation method and a gel method, but any of them may be used. [0028] The size of the voids contained in the fine particles is preferably in the range of several nm to several tens of nm from the viewpoint of effectively absorbing the ink jet ink. The print receiving layer in the present invention contains fine particles and a cationic resin, but in order to effectively obtain the fine voids as described above, the dispersibility and particle size of the fine particles in the ultraviolet curable resin composition are important. .. [0029] The average particle size of the fine particles must be 200 nm or less in order to obtain fine and high porosity. That is, when the average particle size exceeds 200 nm, the voids formed between the fine particles become coarse, the ink absorption capacity and the absorption rate decrease, and sufficient ink acceptability cannot be obtained. In addition, the ultraviolet transmittance becomes low, and the print receiving layer is not sufficiently photocured, so that the inside of the layer is difficult to cure, and the productivity tends to be inferior. The average particle size of the fine particles is preferably 1 to 100 nm, more preferably 2 to 50 nm. When the average particle size is less than 1 nm, the dispersibility in the binder resin tends to decrease, and the voids formed between the particles become too fine, so that sufficient ink acceptability tends not to be obtained. .. [0030] The blending amount of the fine particles in the print receiving layer is 30% by weight or more and less than 100% by weight, preferably 30% by weight or more and 95% by weight or less, more preferably 35% by weight or more, based on the ultraviolet curable resin composition forming the print receiving layer. Weight% or more and 90% by weight or less. If it is less than 30% by weight, it is difficult to form voids of a size required for ink absorption. [0031] It is considered that the cationic resin contained in the ultraviolet curable resin composition has a function of insolubilizing the ink because it imparts water resistance to the image printed by inkjet. Inkjet printer inks generally use anionic water-soluble dyes, and by adding a cationic resin, the dyes in the ink adsorbed in the fine voids can be made insoluble in water, imparting water resistance to the formed image. it can. [0032] The cationic resin that can be used in the present invention is not particularly limited as long as it contains a cationic moiety in the molecule, but the weight average molecular weight is usually in the range of 500 to 200,000, preferably 1,000 to 100,000. If the weight average molecular weight is less than 500, the water resistance of the image tends to be inferior, and if it exceeds 200,000, the binding efficiency with the dye molecule tends to be poor due to steric hindrance of the molecular structure. The effect is reduced. [0033] Examples of cationic resins include cation variants of polyacrylamides, copolymers of acrylamide and cationic monomers, cation-modified products of tertiary amino group-containing (meth) acrylates and copolymers of other common monomers. Examples thereof include polyallylamine, polyaminesulfone, polyvinylamine, polyethyleneimine, polyamide epichlorohydrin, and polyvinylpyridinium halide. Further, a copolymer of a vinylpyrrolidone-based monomer, a vinyloxazolidone-based monomer or a vinylimidazole-based monomer and another general monomer can be mentioned. Further, a copolymer of a cationic variant of a tertiary amino group-containing (meth) acrylate represented by a general formula in JP-A-2000-57635 and another general monomer can be mentioned. [0034] A radical reaction type resin is preferably used as the ultraviolet (UV) curable resin. The radical reaction type UV curable resin is usually prepared by using at least a resin monomer component and a photopolymerization initiator, and if necessary, a resin oligomer component. By selecting various resin monomer components and resin oligomer components, a print receiving layer having various characteristics can be obtained. That is, the viscosity, hardness, and the like 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. [0035] The resin monomer component may be either a monofunctional monomer or a polyfunctional monomer. In order to increase the crosslink density in the print receiving layer and maintain the strength, it is preferable to contain a certain amount of the polyfunctional monomer component. [0036] Examples of the monofunctional monomer include 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, phenoxyethyl acrylate, nonylphenoxyethyl acrylate, N-vinylpyrrolidone, 2-hydroxyethylacryloyl phosphate, and tetrahydrofurfuryl acrylate. , Tetrahydrofurfuryloxyethyl acrylate, tetrahydrofurfuryloxyhexanolide acrylate, acrylate of ε-caprolactone adduct of 1,3-dioxane alcohol, 1,3-dioxolane acrylate and the like. [0037] Examples of the polyfunctional monomer component include cyclopentenyl acrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, tripropylene glycol diacrylate, neopentyl glycol diacrylate, polyethylene glycol (400) diacrylate, and hydroxypivalic acid ester neo. Pentyl 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-dioxandiacrylate, tricyclodecanedimethyloldiacrylate, ε-caprolactone adduct of tricyclodecanedimethyloldiacrylate, trimethylolpropantriacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, Examples thereof include propionic acid / dipentaerythritol triacrylate, hydroxypivalaldehyde-modified dimethylolpropantriacrylate, propionic acid / dipentaerythritol tetraacrylate, and ditrimethylolpropanetetraacrylate. [0038] Examples of the resin oligomer component include acrylic oligomers, ester oligomers, urethane oligomers, ether oligomers and the like. These may be used alone, but when a plurality of types are used in combination, a print receiving layer having different characteristics can be obtained. For example, when an ester-based oligomer is used together with an acrylic-based oligomer, a hard layer can be obtained with excellent water resistance. 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 the urethane-based oligomer is used together with the acrylic-based oligomer, the urethane-based oligomer has a large molecular weight and a small curing shrinkage, so that the possibility of warpage of the substrate is reduced. In this case, the formed cured coating film is relatively soft. [0039] Examples of the above acrylic oligomer include alkyl (meth) such as (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and butyl (meth) acrylate. Acrylate polymer, or the above monomer and aromatic vinyl compounds such as styrene, α-methylstyrene, (o, m, p) vinylphenol, vinylcarboxylic acids such as maleic acid, itaconic acid, crotonic acid, and fumaric acid. Compounds, glycidyl group-containing vinyl compounds such as glycidyl (meth) acrylate, allyl glycidyl ether, glycidyl ethylacrylate, crotonyl glycidyl ether, glycidyl crotonate, aromatic acrylate compounds such as benzyl (meth) acrylate, hydroxyethyl (meth) Substituent alkyl acrylate compounds such as acrylate, N, N-dimethylaminoethyl (meth) acrylate, (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-dimethylaminoethyl Examples thereof include copolymers with compounds selected from acrylamide compounds such as (meth) acrylamide, vinyl acetate, (meth) acrylonitrile, (meth) acrylic acid chloride, N- (meth) acryloylmorpholine and the like. [0040] Examples of the above ester-based oligomer include an ester of a polyester diol composed of a ring-opening polymer of phthalic anhydride and propylene oxide and an acrylic acid, and an ester of a polyester diol composed of 1,6-hexanediol adipic acid and an acrylic acid. Examples thereof include an ester of triol and acrylic acid composed of a reaction product of diethylene glycol trimellitic acid, and an ester of a ring-opening polymer of δ-valerolactone and acrylic acid. [0041] Examples of the urethane-based oligomer include a reaction product of a polyurethane composed of hexamethylene diisocyanate and 1,6-hexanediol and 2-hydroxyethyl acrylate, and a polyester diol composed of adipic acid and 1,6-hexanediol and tolylene. Examples thereof include those obtained by reacting a diisocyanate oligomer that has been reacted with isocyanate with 2-hydroxyethyl acrylate. [0042] Examples of the ether-based oligomer include an ester of polypropylene glycol and acrylic acid. In addition, an epoxy-based oligomer obtained by reacting an epoxy resin with an acrylate, polyarylate, or the like can also be used as a resin oligomer component. [0043] Examples of the photopolymerization initiator include benzoin isopropyl ether, benzophenone, 2-hydroxy-2-methylpropiophenone, 1-hydroxycyclohexylphenylketone, 2,4-diethylthioxanthone, methyl o-henzoyl benzoate, 4,4. -Bisdiethylaminobenzophenone, 2,2-diethoxyacetophenone, benzyl, 2-chlorothioxanthone, diisopropylthiozanson, 9,10-anthraquinone, benzoin, benzoine methyl ether, 2,2-dimethoxy-2-phenylacetophenone, Examples thereof include 2-hydroxy-2-methyl-propiophenone, 4-isopropyl-2-hydroxy-2-methylpropiophenone, α, α-dimethoxy-α-phenylacetone and the like. [0044] In addition to the above, the ultraviolet curable resin composition may contain a polymerization inhibitor, a storage stabilizer, a dispersant, an antifoaming agent, a binder resin other than the ultraviolet curable resin, and the like, if necessary. [0045] An ultraviolet curable screen printing machine is preferably used for forming the print receiving layer in the present invention. Then, in the present invention, a print receiving layer divided into a plurality of regions having different colors is formed by screen printing performed by a manufacturer of an optical recording medium. [0046] For printing performed by the manufacturer of the optical recording medium, appropriate content can be selected according to a design or trademark request. That is, characters, figures, symbols, patterns, colors and the like can be used as display elements. As a method of providing a plurality of regions having different colors on the outermost layer forming surface of the optical recording medium of the present invention, for example, a pigment, a dye, or the like is added to the composition for forming a print receiving layer to the extent that it does not interfere with printing by a later user. It is preferable to use the one to which the colorant of the above is added and to form a print receiving layer by using a plurality of kinds of compositions having different colors. Further, in the normal print receiving layer, a white pigment such as titanium oxide may be blended in order to whiten the ground color. In such a case, the blending amount of the white pigment is different to cause a color difference in the ground color. By forming, it may be divided into a plurality of regions having different colors. [0047] The colorant used in the above composition for forming a print receiving layer is not particularly limited, and red, green, blue, and yellow dyes are used. In addition, metal powders and white pigments are used, if necessary. , Fluorescent pigments and the like can also be used. Specific examples of dyes include Victoria Pure Blue (42595), Auramine O (41000), Cachilon Brilliant Flavin (Basic 13), Rhodamine 6GCP (45160), Rhodamine B (45170), Sakuranin OK 70: 100 ( 50240), Eriograusin X (42080), NO.120 / Rhodamine Yellow (21090), Rhodamine Yellow GRO (21090), Shimura First Yellow GRO (21090), Shimura First Yellow 8GF (21105), Benzidine Yellow 4J- 564D (21095), Simler First Red 4015 (12355), Lionor Red 7B4401 (15850), Firstgen Blue JGR-L (74160), Lionor Blue SM (26150), Lionor Blue ES (Pigment Blue 15: 6,) Pigment Blue 1536), Lionogen Red GD (Pigment Red 168, Pigment Red 108), Rhodamine Green 2YS (Pigment Green 36), etc. (The numbers in parentheses above mean the color index (CI)). .. [0048] As a light source for ultraviolet irradiation, a high-pressure mercury lamp, a metal halide lamp, or the like is used. The amount of irradiation energy is usually 150 to 2000 mJ / cm.², Preferably 250 ~ 1000mJ / cm²It is selected from the range of. At this time, when the screen printing method is used, it is preferable to add a leveling agent for the purpose of smoothing the surface of the coating film, releasing air bubbles from the coating film instantly, and increasing the glossiness of the coating film surface. As the leveling agent, silicon or the like is preferable. [0049] [Example] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist thereof is not exceeded. [0050] Example 1 A solution of the metal-containing azo dye was dropped onto an injection-molded polycarbonate resin substrate (120 mm in diameter) with a groove (groove) having a depth of 1600 Å and a width of 0.45 μm, and applied at a rotation speed of 500 rpm by a spin coating method at 90 ° C. Dry for 30 minutes to form a recording layer. [0051] Next, a silver film having a film thickness of 800 Å (80 nm) is formed on the recording layer by a sputtering method to form a reflective layer. Then, after spin-coating the entire surface of this reflective layer with an ultraviolet curable resin, the entire surface was cured by irradiating with ultraviolet rays to form a protective layer of 5 μm. [0052] Next, the primary particle size is 10 nm and the specific surface area is 250 m.²Using an ultraviolet curable resin composition (A) containing 50% by weight of silica of / g and a composition (B) containing a colorant, the composition (A) is applied to the surface of the protective layer. After the portion excluding the display of "CD-R" was formed by screen printing, the display portion of "CD-R" was formed by screen printing of the composition (B). Then, the resin composition was cured by irradiation with ultraviolet rays to form a print receiving layer having a film thickness of 20 μm divided into two regions having different colors. [0053] As a result of printing on the print receiving layer of the optical recording medium obtained above with the Fargo inkjet printer "CD-Coler Printer", overlay printing is performed on the display portion of the "CD-R" without any problem. I was able to do it. [0054] [Effect of the invention] According to the present invention described above, even though the print receiving layer is divided into a plurality of regions having different colors by printing by a manufacturer of an optical recording medium or the like, subsequent printing by a user or the like can be performed without any trouble. An improved optical recording medium is provided.