JPH11259913A - Optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information record medium having a surface improved in printability by an ink jet printer in particular. SOLUTION: A recording layer capable of recording information by irradiation with a laser beam, a reflection layer and a protective layer are formed in this order on a transparent substrate in this record medium. The record medium is provided with a water absorptive layer having a surface which contains water absorptive particles and a UV curing resin, is free of waving of >=25 μm in amplitude and <=500 μm in period and has a contact angle with water of <=90 deg. on the protective layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat mode optical information recording medium capable of recording and reproducing information by using a laser beam, and more particularly to writing characters and patterns on the surface of the optical information recording medium. The present invention relates to a write-once optical information recording medium that can be used.

[0002]

2. Description of the Related Art Conventionally, an optical information recording medium (write-once type optical disk) on which information can be recorded only once by a laser beam is known as a write-once CD (so-called CD-R). CD-Rs have the advantage that they can be played back using a commercially available CD player. Recently, with the spread of personal computers and the like, CD-Rs have become useful as a medium for storing information and data from them. ing.

A typical structure of a CD-R type optical disk is such that a recording layer made of an organic dye, a reflective layer made of a metal such as gold, and a protective layer made of a resin are laminated in this order on a transparent disk-shaped substrate. Things. Writing (recording) of information on the optical disk is performed by irradiating the optical disk with near-infrared laser light (usually laser light having a wavelength of around 780 nm), and the irradiated portion of the dye recording layer emits the light. Information is recorded by absorbing and locally increasing the temperature, causing a physical or chemical change (for example, formation of pits or the like) and changing its optical characteristics. On the other hand, reading (reproduction) of information is also usually performed by irradiating the optical disc with laser light having the same wavelength as the recording laser light, and the portion where the optical characteristics of the dye recording layer has changed (recording by forming pits or the like). The information is reproduced by detecting a difference in reflectance between a portion (unchanged portion) and a portion that does not change (unrecorded portion).

[0004] In a CD in which information is recorded in advance, titles and various designs are printed on the surface of the protective layer in order to display the information recorded there. Conventionally, for this printing, a screen printing method that is advantageous for printing a large number of identical prints has been used. On the other hand, it is not always advantageous to print using a screen printing method in a CD-R manufactured for a small amount and a variety of uses. Further, since the protective layer is usually formed of a UV curable resin, its surface is often hydrophobic. For this reason, CD-R
When a title or the like is given, a method of using a writing instrument such as an oil-based felt pen on the surface of the protective layer, or pasting a label or the like on the surface is generally used. But,
In such a display means, not only is it troublesome, but the display becomes irregular, or when a label is attached,
In some cases, the label peeled off in the apparatus during storage or during recording / reproduction.

[0005] In recent years, printing methods using an ink jet printer have become widespread. Printing by an ink-jet printer is excellent in terms of easy colorization, low cost, and easy operation. Therefore, a printing method using an inkjet printer has been proposed as a printing method on a CD-R as described above. In printing by an ink jet printer, an aqueous ink is usually used. Therefore, various improvements are required so that the aqueous ink can be fixed on the surface of the protective layer.

Japanese Patent Application Laid-Open No. 6-60432 discloses a CD-R in which the surface on the side where the protective layer is provided has a hydrophilic surface so that the printing ink can be fixed thereon. The hydrophilic surface has a fine rough surface due to the organic or inorganic pigment dispersed in the hydrophilic resin film, and has a configuration in which the aqueous ink is easily fixed. Specifically, the average particle diameter is about 4 μm in a hydrophilic resin such as polyvinylpyrrolidone.
Examples of CD-Rs provided with a hydrophilic resin film containing and dispersing synthetic amorphous finely-divided silica are described. JP 7
JP-169100 discloses a CD-R in which a protective layer located on the uppermost layer is made of a UV curable resin containing an organic filler and an inorganic filler, and the surface of the protective layer is a surface suitable for printing. . And here, 10 μm
Organic fillers (eg, protein) and inorganic fillers (eg, synthetic silica) having a relatively large average particle size as described above
Is described in a UV-curable resin. JP-A-8-22641 discloses a CD-R in which a surface layer containing a filler such as silica protruding from the surface is provided on a protective layer.

[0007]

SUMMARY OF THE INVENTION The present inventor has mainly studied a CD-R having a surface layer suitable for printing by an ink jet printer and capable of printing with good image quality. According to the study, even a CD-R having a surface layer improved so that the aqueous ink is easily fixed as described above has a good image quality with almost no color unevenness and bleeding, and after printing. In order to achieve printing where the ink dries quickly,
It has been found that the wettability of the surface and the shape of the surface require further improvement. That is, Japanese Patent Application Laid-Open No.
In the case of the surface layer described in JP-A No. 2 (KOKAI), the ink is easily wetted because it is formed from a hydrophilic resin and has a rough surface due to a filler, but it still has a sufficient water absorption point. is not. For this reason, the ink hardly dries after printing, which hinders subsequent handling, or it takes a long time to fix the ink, which tends to cause color unevenness. Further, in the case of the surface layer described in JP-A-7-169100 or JP-A-8-22641, it is still not sufficient in that quick absorption of aqueous ink is required, and filler is not provided on the surface layer. Since relatively large projections and depressions are formed (that is, large undulations are formed), there is a problem that color unevenness and bleeding easily occur along the projections and depressions.

An object of the present invention is to provide an optical information recording medium having improved surface printability. The present invention provides an optical information having a surface layer capable of printing with good image quality with less color unevenness and bleeding, particularly with an ink jet printer, and furthermore, drying of an aqueous ink after printing is quick and handling after printing is easy. It is intended to provide a recording medium.

[0009]

According to the research of the present inventors,
In order for the printing with the water-based ink to be performed well, the printing surface has a high water absorption so that the printing surface is easily wetted, and the surface is flat and uneven so that color unevenness does not occur. It turned out that it was necessary to be in a good state. As a result of further research by the present inventors, in order to form a layer having such surface characteristics, a surface layer (water-absorbing layer), which is a printing surface, is composed of water-absorbing particles and an ultraviolet curable resin. Using water-absorbing particles having a relatively small average particle size compared to this layer thickness suppresses the roughness of the surface layer, and by using a relatively large amount of these particles, it becomes easy to wet the aqueous ink. As a result, it has been found that a surface layer suitable for printing by an inkjet printer can be obtained.

The present invention provides an optical information recording medium comprising a recording layer, a reflective layer and a protective layer, on which information can be recorded by irradiating a laser beam on a transparent substrate in this order. On the layer, there is provided a water-absorbing layer having a surface containing water-absorbing particles and an ultraviolet curable resin, having a surface having an amplitude of 25 μm or more and a cycle of 500 μm or less, and a contact angle with water of 90 ° or less. An optical information recording medium characterized in that:

The optical information recording medium of the present invention preferably has the following aspects. (1) The contact angle of the surface of the water absorbing layer with water is 40 to 90 degrees (more preferably 50 to 87 degrees, particularly 60 to 85 degrees).
Degree). (2) The water-absorbing particles are organic fine powder composed of cellulose acetate or protein. Proteins are particularly preferred. (3) The average particle size of the water-absorbing particles is in the range of 1 to 8 μm (more preferably, 3 to 8 μm). (4) The water-absorbing layer is composed of the water-absorbing particles and the ultraviolet curable resin.
0: 70-80: 20 (more preferably, 35: 65-
70:30) by weight. (5) The thickness of the water-absorbing layer is in the range of 10 to 20 μm (more preferably, 12 to 18 μm). (6) The ratio of the average particle diameter of the water-absorbing particles to the layer thickness of the water-absorbing layer is 1/5 to 1/2 (more preferably, 1/4 to 1/2,
Especially 1/4 to 1 / 2.5).

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The optical information recording medium of the present invention has a recording layer, a reflective layer, and a protective layer laminated in this order on a transparent substrate. The present invention is characterized in that a water absorbing layer having an excellent specific structure is provided. less than,
A method for producing the optical information recording medium of the present invention including a transparent substrate, a recording layer, a reflective layer, a protective layer, and a water absorbing layer will be described in order.

The transparent substrate can be arbitrarily selected from various materials used as a substrate of a conventional optical information recording medium. Examples of the substrate material include glass; polycarbonate; acrylic resins such as polymethyl methacrylate; vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymer; epoxy resins; amorphous polyolefins and polyesters. These materials may be used together if desired. Note that these materials can be used in the form of a film or a rigid substrate. Among the above materials, polycarbonate is preferred from the viewpoints of moisture resistance, dimensional stability, cost, and the like.

An undercoat layer may be provided on the surface of the substrate on which the recording layer is provided, for the purpose of improving flatness, improving adhesion, and preventing deterioration of the recording layer. Examples of the material of the undercoat layer include polymethyl methacrylate, acrylic acid,
Methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylol acrylamide, styrene / vinyl toluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide And high molecular substances such as vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene, polypropylene and polycarbonate; and surface modifiers such as silane coupling agents.

The undercoat layer is prepared by dissolving or dispersing the above substances in an appropriate solvent to prepare a coating solution, and then applying this coating solution to the substrate surface by using a coating method such as spin coating, dip coating, or extrusion coating. Can be formed. The thickness of the undercoat layer is generally 0.005.
-20 μm, preferably 0.01-10 μm
m.

On the substrate (or undercoat layer), it is preferable to form a tracking groove or an unevenness (pre-groove) representing information such as an address signal. This pregroove is preferably formed directly on the substrate when injection molding or extrusion molding of a resin material such as polycarbonate.

The pre-groove may be formed by providing a pre-groove layer. As a material for the pregroove layer, a mixture of at least one monomer (or oligomer) of acrylic acid monoester, diester, triester and tetraester and a photopolymerization initiator can be used. The formation of the pre-groove layer is performed, for example, by first forming a precisely formed master (stamper).
A mixture of the above-mentioned acrylate and the polymerization initiator is applied thereon, and after further placing the substrate on the coating solution layer, the coating layer is cured by irradiating ultraviolet rays through the substrate or the matrix. To fix the substrate and the coating layer.
Next, it can be obtained by peeling the substrate from the matrix. The thickness of the pre-groove layer is generally 0.05 to 1
It is in the range of 00 μm, preferably in the range of 0.1 to 50 μm.

The depth of the pregroove is 0.01 to 0.3 μm
m is preferable, and the half width is
It is preferably in the range of 0.2 to 0.9 μm. By setting the depth of the pre-groove layer in the range of 0.15 to 0.2 μm, the sensitivity can be improved without substantially lowering the reflectance, which is particularly preferable. Therefore, such an optical disk (an optical disk in which a dye recording layer and a light reflecting layer are formed on a deep groove substrate) has a high sensitivity, so that it is possible to perform recording even with a low laser power, and thereby an inexpensive semiconductor laser is used. There is an advantage that the semiconductor laser can be used or the service life of the semiconductor laser can be extended.

A recording layer is provided on the substrate. The recording layer in the optical information recording medium of the present invention is made of a dye, and the dye used is not particularly limited. For example, cyanine dyes, phthalocyanine dyes, imidazoquinoxaline dyes, pyrylium / thiopyrylium dyes, azurenium dyes, squalilium dyes, Ni, Cr
Such as metal complex dyes, naphthoquinone dyes, anthraquinone dyes, indophenol dyes, merocyanine dyes, oxonol dyes, naphthoaniline dyes,
Triphenylmethane dye, triallylmethane dye,
Aminium and diimmonium dyes and nitroso compounds can be mentioned. Among these dyes, cyanine dyes, phthalocyanine dyes, azulhenium dyes, squalilium dyes, oxonol dyes, and imidazoquinoxaline dyes are preferred. Particularly preferred are cyanine dyes. These cyanine dyes are described in, for example, the above-mentioned JP-A-4-175188.

The dye recording layer can be formed by dissolving the dye in a solvent to prepare a coating solution, applying the coating solution on the substrate surface to form a coating film, and then drying. In preparing the coating solution, it is preferable to add a discoloration inhibitor, and if desired, a binder may be added. When an anti-fading agent is used in combination, the amount used is usually in the range of 0.1 to 50% by weight, preferably 0.5 to 45% by weight, more preferably the amount of the dye. Ranges from 3 to 40% by weight, in particular from 5 to 25% by weight.

Examples of the solvent for the coating solution for the dye recording layer include:
Esters such as butyl acetate and cellosolve acetate; ketones such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone; chlorinated hydrocarbons such as dichloromethane, 1,2-dichloroethane and chloroform; amides such as dimethylformamide; hydrocarbons such as cyclohexane; tetrahydrofuran; Ethers such as ethyl ether and dioxane; alcohols such as ethanol, n-propanol, isopropanol, n-butanol and diacetone alcohol; fluorinated solvents such as 2,2,3,3-tetrafluoropropanol; ethylene glycol monomethyl ether, ethylene Examples thereof include glycol ethers such as glycol monoethyl ether and propylene glycol monomethyl ether. The above-mentioned solvents can be used alone or in combination of two or more in consideration of the solubility of the dye used. Various additives such as an antioxidant, a UV absorber, a plasticizer, and a lubricant may be further added to the coating solution according to the purpose.

Typical examples of the anti-fading agent include nitroso compounds, metal complexes, diimmonium salts, aminium salts and the like. These examples are disclosed in
No. 300288, No. 3-224793, or No. 4
No. 146189.

Examples of binders include, for example, gelatin,
Natural organic high molecular substances such as cellulose derivatives, dextran, rosin, and rubber, and hydrocarbon resins such as polyethylene, polypropylene, polystyrene, and polyisobutylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl chloride / polyvinyl acetate copolymer Such as vinyl resins, polymethyl acrylate, acrylic resins such as polymethyl methacrylate, polyvinyl alcohol, chlorinated polyethylene,
Examples include synthetic organic polymers such as epoxy resins, butyral resins, rubber derivatives, and initial condensates of thermosetting resins such as phenol / formaldehyde resins. When a binder is used as a material for the dye recording layer, the upper limit of the amount of the binder used should be 20 parts by weight, preferably 10 parts by weight, more preferably 5 parts by weight, based on 100 parts by weight of the dye. It is.

The concentration of the dye in the coating solution for the dye recording layer thus prepared is generally in the range of 0.01 to 10% by weight, preferably in the range of 0.1 to 5% by weight.

Examples of the coating method include a spray method, a spin coating method, a dip method, a roll coating method, a blade coating method, a doctor roll method, and a screen printing method. The dye recording layer may be a single layer or a multilayer. The thickness of the recording layer (after drying) is generally 20 to 500 nm.
And preferably in the range of 50 to 300 nm.

On the recording layer, a reflective layer is provided for the purpose of improving the reflectivity especially at the time of reproducing information. The light-reflective substance that is the material of the reflection layer is a substance having a high reflectance to laser light, and examples thereof include Mg, Se,
Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo,
W, Mn, Re, Fe, Co, Ni, Ru, Rh, P
d, Ir, Pt, Cu, Ag, Au, Zn, Cd, A
1, Ga, In, Si, Ge, Te, Pb, Po, S
Metals such as n and Bi and semimetals or stainless steel can be mentioned. These substances may be used alone, or in combination of two or more kinds, or may be used as an alloy. Of these, preferred are Cr,
Ni, Pt, Cu, Ag, Au, Al and stainless steel. Particularly preferred are Au metal, Ag metal, and alloys thereof. Preferred Au or Ag alloys include alloys containing at least one metal selected from the group consisting of Pt, Cu, and Al, respectively. The reflective layer can be formed on the recording layer by, for example, vapor deposition, sputtering, or ion plating of a light reflective substance. The thickness of the reflective layer is generally in the range of 10 to 800 nm, preferably in the range of 20 to 500 nm, more preferably 50 to 3 nm.
The range is 00 nm.

A protective layer is provided on the reflective layer for the purpose of physically and chemically protecting the recording layer and the like. This protective layer can also be provided on the side of the substrate on which the recording layer is not provided for the purpose of improving the scratch resistance and moisture resistance. Examples of the material used for the protective layer include SiO, SiO ₂ , and Mg.
Examples thereof include inorganic substances such as F ₂ , SnO ₂ , and Si ₃ N ₄ , and organic substances such as a thermoplastic resin, a thermosetting resin, and a UV-curable resin. The protective layer can be formed, for example, by laminating a film obtained by extrusion of a plastic on the reflective layer and / or the substrate via an adhesive. Alternatively, it may be provided by a method such as vacuum deposition, sputtering, or coating. In the case of a thermoplastic resin or a thermosetting resin, they can also be formed by dissolving these in an appropriate solvent to prepare a coating solution, applying the coating solution, and drying. U
In the case of a V-curable resin, a coating solution is prepared as it is without using a solvent or by dissolving it in an appropriate solvent, and then the coating solution is applied and cured by irradiating UV light. Can be. Various additives such as an antistatic agent, an antioxidant, and a UV absorber may be added to these coating solutions according to the purpose. The thickness of the protective layer thus formed is generally 0.1 to 100 μm.
In the range.

A water absorbing layer is provided on the protective layer. The water-absorbing layer is composed of water-absorbing particles and an ultraviolet curable resin, and has a surface with an amplitude of 25 μm or more and a cycle of 500 μm or less without undulation, and a contact angle with water of 90 ° or less. . The surface of the water absorbing layer has a contact angle with water of 4
0 to 90 degrees (more preferably 50 to 87 degrees, particularly 6
(0 to 85 degrees). By setting the contact angle with water in such a specific range, the surface of the water-based ink can be easily applied to the surface, and a surface having good printability without color unevenness can be obtained. The water absorbing layer having such characteristics can be formed, for example, by the following method.

The water-absorbing particles are not particularly limited as long as they are particles capable of absorbing moisture, but are preferably formed by processing a water-absorbing material into a fine powder. Examples of such water-absorbing particles include monosaccharides such as glucose, disaccharides such as sucrose and maltose, and polysaccharides such as cellulose and starch; inorganic cellulose esters such as cellulose sulfate and cellulose phosphate; Mention may be made of organic cellulose esters such as cellulose and cellulose acetate, and cellulose derivatives such as cellulose ethers such as sodium carboxymethylcellulose and hydroxyethylcellulose; and natural polypeptides and proteins. Of these, cellulose acetate and protein are preferred. Particularly preferred are proteins.

The water-absorbing particles preferably have such a size that they do not protrude from the surface of the water-absorbing layer when contained in the water-absorbing layer. Specifically, the average particle diameter of the water-absorbing particles is preferably in the range of 1 to 8 μm (more preferably, 3 to 8 μm). The ratio between the average particle diameter of the water-absorbing particles and the thickness of the water-absorbing layer is １ ／ to （(more preferably １ ／ to 、, particularly １ ／ to １ ／). .5)
Is preferably within the range.

By using an ultraviolet curable resin as a binder for the water absorbing layer, the water absorbing layer can be easily formed, which is advantageous in production. UV-curable resins are generally composed of monomers or oligomers of polymerizable compounds having one or more reactive acrylic groups in the molecule, or mixtures thereof, reaction initiators and reaction catalysts, and have conventionally been used as UV-curable resins. It can be used by selecting from known ones. In addition, a material having a small curing shrinkage is selected so as not to deform the product. For example, as monofunctional monomers, tetrahydrofurfuryl acrylate, ethyl carbitol acrylate, dicyclopentyloxy acrylate, phenyl carbitol acrylate, nonylphenoxyethyl acrylate, hydroxyethyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, Acrylamide, acroylmorpholine, dimethylacrylamide, diethylacrylamide, N-vinylpyrrolidone can be mentioned. Examples of the polyfunctional acrylate include polyol polyacrylate, polyester acrylate, epoxy acrylate, urethane acrylate, pentaerythritol di (tri) acrylate, N, N'-methylenebisacrylamide, hexamethylenebisacrylamide and the like. Preferable examples include a monofunctional or polyfunctional monomer or oligomer having a polar group such as an acrylamide group, a vinylamino group, or a hydroxyl group.

Examples of the photopolymerization initiator include benzoin or its ethers such as benzoin, benzoin methyl ether, benzoin ethyl ether and benzoin isopropyl ether, benzophenone compounds such as benzophenone, and benzyl compounds such as benzyl, benzyl methyl ketal and benzyl ethyl ketal. Compound, 1-phenyl-
Examples thereof include hydroxyalkyl phenyl ketone compounds such as 2-hydroxy-2-methyl-2-propane.

The water-absorbing layer is prepared by mixing and dispersing the above-mentioned ultraviolet-curable resin and water-absorbing particles with an organic solvent, if necessary, to prepare a coating solution for forming a water-absorbing layer. Can be formed. The application method is not particularly limited, but a method by screen printing is advantageous. The water-absorbing layer is preferably formed such that the water-absorbing particles and the ultraviolet curable resin are formed in a weight ratio of 30:70 to 80:20, and is formed in a weight ratio of 35:65 to 70:30. More preferred. The layer thickness of the water-absorbing layer is 10 to 20 μm (more preferably, 12 to 18 μm).
m).

The optical information recording medium of the present invention may be a single plate having the above-described structure, or two substrates having the above-mentioned structure may be arranged such that the recording layer is on the inside and the adhesive By bonding using such a method, a bonding type optical information recording medium can be obtained. Alternatively, an air-sandwich type optical information recording medium is formed by bonding a substrate having the above structure to at least one of two disk-shaped substrates via a ring-shaped inner spacer and a ring-shaped outer spacer. It can also be done. Further, the configuration of the present invention can also be used for a DVD-R type optical information recording medium.

Recording and reproduction of optical information using the optical information recording medium of the present invention are performed, for example, as follows. The optical information recording medium of the present invention is capable of recording and reproducing at 1 × speed (1.2 to 1.4 m / sec) of a normal CD format, and at 4 × speed, 6 × speed or higher. Recording / reproduction is also possible.

First, while rotating the optical information recording medium at a predetermined constant linear velocity (1.2 to 14 m / sec in the case of the CD format) or a predetermined constant angular velocity, a medium for recording semiconductor laser light or the like from the substrate side. Of light. By this light irradiation, the irradiated portion of the recording layer absorbs the light and locally raises the temperature, and pits are generated to record information by changing its optical characteristics. 500n as recording light
A semiconductor laser beam having an oscillation wavelength in the range of m to 850 nm is used. The laser beam wavelength used is preferably 500 nm or more and 800 nm or less.
In a CR-D type optical information recording medium, 770 to 79
Wavelengths in the range of 0 nm are suitable. Reproduction of the information recorded as described above, irradiating the semiconductor laser light from the substrate side while rotating the optical information recording medium at a predetermined linear speed,
This can be performed by detecting the reflected light.

[0037]

[Embodiment 1]

[0038]

Embedded image

The above-mentioned indolenine-based cyanine dye A and 10% by weight of the dye and 2,2 ',
It was dissolved in 3,3′-tetrafluoropropanol to prepare a coating solution for forming a recording layer (concentration of the coating solution: 2.5% by weight).

This coating solution is applied to the surface of a spiral pre-groove (track pitch: 1.6 μm, pre-groove width: 0.4 μm, pre-groove depth: 0.16 μm).
On the surface of the pregroove side of a polycarbonate substrate (diameter: 120 mm, thickness: 1.2 mm, manufactured by Teijin Limited, trade name: Panlite AD5503) formed by injection molding, at a rotation speed of 300 rpm to 2000 rpm. The dye recording layer (thickness (within the pre-groove): about 150 nm) was formed by spin coating and drying while changing the thickness.

Next, Au is sputtered on the recording layer,
A reflective layer having a thickness of about 100 nm was formed. Further, on the reflective layer, a UV curable resin (trade name: Daikyu Clear SD)
-2003, manufactured by Dainippon Ink and Chemicals, Inc.) by spin coating at a rotation speed of 100 rpm to 2000 rpm.
m and then irradiated with ultraviolet light from a high-pressure mercury lamp to cure the coating, thereby forming a protective layer having a thickness of about 7 μm.

On the thus obtained protective layer, a water-absorbing layer was formed by the following procedures 1) to 3). 1) Preparation of UV Curable Resin The following components were mixed to prepare a UV curable resin. Acrylic acrylate 16% by weight Aliphatic (chain) monomer 50% by weight Alicyclic monomer 25% by weight Photopolymerization initiator 2% by weight Auxiliary agent 7% by weight Viscosity of ultraviolet curable resin: 50 to 58 cps Viscometer: cone Flat type rotational viscometer (Tokyo Keiki Co., Ltd.)
Measurement temperature: 25 ° C. (The following viscosities were measured in the same manner as above.)

2) Preparation of Coating Solution for Forming Water Absorbing Layer The obtained ultraviolet curable resin and water absorbing particles (protein powder, average particle size: 5 μm) were mixed at a ratio of 60:40 (weight ratio), A coating liquid for forming a water-absorbing layer was prepared (viscosity: 95 to 100 cps).

3) Formation of Water Absorbing Layer The obtained coating solution was applied on the protective layer using a 300-mesh screen. Next, the coating layer was irradiated with UV light under the following irradiation conditions and cured to form a water absorbing layer having a thickness of about 13 μm. UV light irradiation conditions: metal halide lamp 80W / cm
^2. Two lamps with lamp power of 400W, lamp height 15
cm, belt speed 10 m / min, integrated light amount: about 240 mJ / cm ² or more, according to the present invention, comprising a substrate, a recording layer, a reflective layer, a protective layer and a water-absorbing layer laminated in this order.
An R-type optical information recording medium (hereinafter, an optical disk) was manufactured.

Example 2 A CD-R type optical disk according to the present invention in the same manner as in Example 1 except that a water-absorbing layer was formed using cellulose acetate (average particle diameter: 7 μm) as the water-absorbing particles. Was manufactured. At this time, the viscosity of the coating liquid for forming a water-absorbing layer was 92 to 98 cps.

Example 3 A CD-R type optical disk according to the present invention was manufactured in the same manner as in Example 1, except that a reflective layer having a thickness of 150 nm was provided using Ag instead of Au.

[Embodiment 4] In Embodiment 3, the recording layer,
A CD-R type optical disk according to the present invention was manufactured in the same manner except that the coating solution prepared as described below was used for preparing the water absorbing layer. (Preparation of coating solution for recording layer)

[0048]

Embedded image

The above-mentioned indolenine-based cyanine dye C and 10% by weight based on the dye of 2,2 ',
It was dissolved in 3,3′-tetrafluoropropanol to prepare a coating solution for forming a recording layer (concentration of the coating solution: 2.5% by weight).

(Preparation of Coating Solution for Water Absorbing Layer) 1) Preparation of UV-Curable Resin The following components were mixed to prepare a UV-curable resin. Polyvinyl special acrylate 45% by weight Urethane oligomer 4% by weight Alicyclic monomer 27% by weight Aliphatic (chain) monomer 19% by weight Photopolymerization initiator 4% by weight Auxiliary 1% by weight Viscosity of ultraviolet curable resin: 60 ~ 63 cps

2) Preparation of coating liquid for forming water-absorbing layer The obtained ultraviolet-curable resin and water-absorbing particles (protein powder, average particle diameter: 5 μm) were mixed at a ratio of 65:35 (weight ratio), A coating liquid for forming a water-absorbing layer was prepared (viscosity: 90 to 95 cps).

[Comparative Example 1] In Example 1, 20 μm was used instead of protein particles having an average particle diameter of 5 μm.
The same amount of protein particles having an average particle diameter of m is used to prepare a coating liquid for forming a water-absorbing layer, and a coating liquid having a thickness of 17
A CD-R optical disc for comparison was manufactured in the same manner except that a water absorbing layer of μm was formed. In addition, 20 μm
Of the water-absorbing layer-forming coating liquid prepared using the same amount of protein particles having an average particle diameter of 98 to 102 cp
s.

[Comparative Example 2] In Example 1, no protein particles having an average particle size of 5 μm were used.
That is, a CD for comparison was prepared in the same manner except that a water-absorbing layer having a thickness of 16 μm comprising only an ultraviolet curable resin was formed.
-An R type optical disk was manufactured.

Comparative Example 3 A coating liquid for forming a water-absorbent layer was prepared by mixing an ultraviolet-curable resin and protein particles having an average particle diameter of 5 μm in a ratio of 4: 1 (weight ratio) in Example 1. Was prepared in the same manner except that a water-absorbing layer having a thickness of 15 μm was formed using this.
An R-type optical disk was manufactured. At this time, the viscosity of the coating liquid for forming a water-absorbing layer was 75 to 80 cps.

Comparative Example 4 In Example 1, 10 μm of protein particles having an average particle size of 5 μm were used instead of 10 μm.
m, and a UV-curable resin and the protein particles are mixed at a ratio of 10: 1 (weight ratio) to prepare a coating liquid for forming a water-absorbing layer. A CD-R optical disc for comparison was manufactured in the same manner except that a water-absorbing layer having a thickness of 15 μm was formed. At this time, the viscosity of the coating liquid for forming a water-absorbing layer was 65 to 68 cps.

The characteristics of the water absorbing layers of the optical disks obtained in Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 1 below.

[0057]

[Table 1] Table 1 Average particle size Water-absorbing particles: UV Resin layer thickness Water-absorbing particles (μm) (weight ratio) (μm) ────────────────────────────────── Example 1 Protein powder 5 40:60 13 Example 2 Cellulose acetate powder 7 40:60 13 Example 3 Protein powder 5 40:60 13 Example 4 Protein powder 5 35:65 13 ───────────────────────────── Comparative Example 1 Protein powder 20 40:60 17 Comparative Example 2 Not added-0: 100 16 Comparative Example 3 Protein Powder 5 20:80 15 Comparative Example 4 Protein Powder 10 10: 100 15 ────────────────────── UV resin: UV-curable resin

[Evaluation as Optical Information Recording Medium] The optical discs obtained in Examples and Comparative Examples were evaluated for the surface characteristics of the water absorbing layer by the following method. In addition, printing was performed on the surface of the water-absorbing layer by an inkjet printer, and the printed image was evaluated.

(1) Measurement of surface undulation of water-absorbent layer The surface undulation of the water-absorbent layer was measured using DEKTAKII (a stylus type undulation meter) manufactured by Soloan. The measurement of waviness was performed in the following procedure. First, as shown in FIG. 1, four lines are drawn on the water-absorbing layer of the optical disk so as to divide the layer into eight equal parts and pass through the center. next,
Draw a circle with a radius of 40 mm from the center, and identify eight points that intersect the four lines described above. Then, the needle of the above-mentioned waviness measuring device is placed at these eight points, and the wave shape when the needle is slid while being in contact with the needle in the circumferential direction of 1 mm from here is measured. The average value of the undulation at these eight points was calculated, and the amplitude was 25.
The presence or absence of undulations having a period of 500 μm or more and a period of 500 μm or more was examined.

(2) Measurement of contact angle with water on the surface of the water-absorbing layer The contact angle was measured at 25 ° C. using a commercially available contact angle measuring device.

(3) Evaluation of Printed Image by Inkjet Printer 1) Evaluation of color unevenness Solid printing was performed on the water-absorbing layer using an inkjet printer. The printed image was observed, and color unevenness was evaluated based on the following criteria. Further, the time a until the ink dries after printing is measured. Water-based inkjet printer model: EPSON Corporation
Manufacture, MJ-500C Evaluation criteria for printed images A: Color unevenness is hardly observed B: Small color unevenness is observed C: Ink is not fixed on the surface by repelling ink

2) Evaluation of bleeding Thin characters (0.5 mm) were printed on the water-absorbing layer using an ink jet printer. The printed state of the character was observed, and the bleeding was evaluated according to the following criteria. After printing, the time b until the ink dries was measured. Aqueous inkjet printer model: Same model as above. Evaluation criteria for print condition AA: Few bleeding is observed, and fine characters are printed. BB: Bleeding is slightly observed. The above evaluation results are shown in Table 2. In Table 2, “simultaneous” in the column of the drying time “b” indicates that the ink dried almost at the same time as the end of printing.

[0063]

[Table 2] Table 2 の With water on the surface of the water absorbent layer Evaluation by ink jet printer Amplitude of undulation Contact angle Dry Dry ≦ 500μm 500μm <Color unevenness Time a Bleed time b ────────────────────────────例 Example 1 6 μm 8 μm 80 ° A 30 seconds AA Simultaneous Example 2 5 μm 7 μm 80 ° A 50 seconds AA Simultaneous Example 3 7 μm 7 μm 80 ° A 30 seconds AA Simultaneous Example 4 8 μm 8 μm 80 ° A 30 seconds AA simultaneous ──────────────────────────────────── Comparative Example 1 40 μm 10 μm 85 ° B 60 seconds No measurement Comparative Example 2 7 μm 6 μm 110 ° C-No measurement Comparative Example 3 5 μm 5 μm 100 ° B 10 minutes BB 2 minutes Comparative Example 8μm 7μm 100 ° B 15 minutes BB 2 minutes ────────────────────────────────────

From the results shown in Table 2 above, it is found that the optical disk having a water-absorbing layer having no surface waviness and having a small contact angle with water (that is, having a good water-absorbing property) as defined in the present invention (Examples 1 to 4). In the case of (2), it can be seen that printing can be performed in a favorable state with almost no color unevenness or ink bleeding, and the drying time of the ink is short, so that a clear printed image can be obtained.

On the other hand, in the case of the optical disk of Comparative Example 1,
The water-absorbing layer has a small contact angle with water and shows relatively good water absorption, but since a relatively large undulation is formed on the surface, color unevenness occurs and a satisfactory image quality can be obtained. Can not. In the case of the optical disk of Comparative Example 2 containing no water-absorbing particles, there is no particular waviness on the surface, but since the contact angle with water is large (poor water absorption), color unevenness and bleeding occur. Similarly, in the case of the optical disks of Comparative Examples 3 and 4 having the water-absorbing layer having a large contact angle with water, the printing ink is hard to dry in any case, and color unevenness and ink bleeding occur.

[0066]

The optical information recording medium of the present invention is provided with a surface layer particularly suitable for printing (printing) characters and designs by an ink jet printer, so that good image quality without color unevenness or bleeding occurs. And the ink dries quickly after printing, so that there is no trouble in handling the optical information recording medium after printing.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a position for measuring the undulation of the surface of a water absorbing layer of an optical information recording medium.

Claims (6)

[Claims] 1. An optical information recording medium comprising a transparent substrate on which a recording layer capable of recording information by irradiating a laser beam, a reflective layer and a protective layer are laminated in this order. The water-absorbing layer containing a water-absorbing particle and an ultraviolet curable resin, having an amplitude of not less than 25 μm and a cycle of not more than 500 μm, and having a surface having a contact angle with water of 90 ° or less. Characteristic optical information recording medium. 2. The optical information recording medium according to claim 1, wherein the water-absorbing particles are organic fine powder comprising cellulose acetate or protein. 3. The optical information recording medium according to claim 1, wherein the thickness of the water absorbing layer is in the range of 10 to 20 μm. 4. The optical information recording medium according to claim 1, wherein the average particle diameter of the water-absorbing particles is in the range of 1 to 8 μm. 5. The optical information recording medium according to claim 1, wherein the water absorbing layer contains the water absorbing particles and the ultraviolet curable resin in a weight ratio of 30:70 to 80:20. 6. The optical information recording medium according to claim 1, wherein the ratio between the average particle diameter of the water-absorbing particles and the thickness of the water-absorbing layer is in the range of 1/5 to 1/2.