JPH0316697B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a high-performance information recording medium, particularly an optical information recording medium. BACKGROUND OF THE INVENTION Due to advances in optical technology, information recording media such as video discs and audio discs using large capacity recording and reproducing technology are a field that has rapidly developed in recent years. Regarding the construction method of the disk, the form and each constituent material were considered from various aspects.
Although there are a wide variety of optical disks, a common example of an optical disk is one that has a multilayer structure including three main layers: a substrate, an information recording layer, and a light reflective layer.The substrate is lightweight and easy to handle. Transparent sheets or films made of synthetic resin are often used due to their nature. However, these synthetic resin sheets and film substrates have poor surface scratch resistance and are easily scratched during disk manufacturing and handling.
A major drawback is that recording and reproducing performance tends to deteriorate due to noise generation. Various studies have been carried out to improve these shortcomings, such as providing a transparent layer with a depth of focus greater than the depth of focus of the optical system between the photosensitive layer, that is, the information recording layer, and the substrate, and providing a wear-resistant protective layer on the surface of the substrate. Methods for providing such information have been proposed. However, a mere ordinary transparent coating layer has completely insufficient scratch resistance, and even conventional wear-resistant protective layers do not necessarily have sufficient scratch resistance. Moreover, since these are essentially cross-linked cured films, a drawback has been recognized that the adhesion with the information recording layer is reduced. The present invention improves the drawbacks of these conventional methods and provides a method for producing a new information recording medium that has excellent scratch resistance and adhesion to the information recording layer, is smooth, and is suitable for precise recording and reproduction of information. The main purpose is to That is, in the present invention, a photopolymerizable (meth)acrylate-based curing liquid made of specific components is applied to both sides of a synthetic resin board, and then, in a first step, a half-stage cured film is applied to at least one surface of the resin board. A fluid molding resin is provided on the cured film of the half stage, a master mold is placed on the fluid molding resin, and then active energy rays are irradiated through the resin plate to form the half stage. The key point is to completely cure the cured film on the stage and the fluid molding resin at the same time. The synthetic resin board used in the present invention may be a known methacrylic resin board such as polymethyl methacrylate or methyl methacrylate copolymer, or a known vinyl chloride resin board such as polyvinyl chloride or vinyl chloride copolymer. A resin plate is preferably used, and a methacrylic resin plate is most desirable from the viewpoint of transparency. However, transparent sheets and films made of polystyrene, styrene copolymer, polyester, polycarbonate, etc. can also be used as the synthetic resin plate of the present invention. The (meth)acrylate curing liquid applied to the synthetic resin board needs to be crosslinked and cured by active energy rays. Generally, a method for forming a wear-resistant protective layer is to apply a silicone-based, melamine-based, or urethane-based coating material to a synthetic resin plate and heat cure it, but these methods require high-temperature, long-term curing. This method is unsuitable as a surface treatment method for a resin plate for information disks, which particularly requires smoothness, since the productivity is poor and the resin plate is deformed by heating. In this point,
A photocuring method using active energy rays is preferable because it causes less thermal deformation, but regardless of whether it is a thermosetting method or a photocuring method, the cured film obtained by the conventional method is a crosslinked film, so both lipophilic and hydrophilic compounds have poor wetting. Furthermore, when applying a photosensitive resin to form an information recording layer on the surface of the cured film, it is difficult to apply it uniformly and the adhesion is poor, making the disc unusable. Summer. Of course, adhesion can be improved by reducing the crosslinking density of the cured film, but in this case, as with general paints, the scratch resistance will be significantly reduced, causing noise when playing the disc. Easy to cause scratches. In contrast, the method of the present invention uses a photopolymerizable (meth)acrylate-based curing liquid consisting of specific components, forms an information recording layer on the half-stage cured film through two-step irradiation with active energy rays, and then By completing curing, both interlayer adhesion and scratch resistance between the cured film layer and the information recording layer are achieved. The photopolymerizable (meth)acrylate curing liquid used in the present invention is composed of 30 to 90 parts by weight of a polyfunctional monomer (a) having 3 or more (meth)acryloyloxy groups per molecule and 1 1-2 having 1 or 2 (meth)acryloyloxy groups per molecule
5 to 90 parts by weight of a monomer mixture (A) consisting of 10 to 70 parts by weight of the functional monomer (b) and at least one organic solvent that is mixed with the mixture (A) to form a homogeneous solution. (B)95
~10 parts by weight and 0 to 10 parts by weight of photosensitizer (C) (the above mixture
(A) and organic solvent (B) (based on a total of 100 parts by weight), and can form a crosslinked cured film with excellent wear resistance by irradiation with active energy rays. The polyfunctional monomer (a) having three or more (meth)acryloyloxy groups per molecule used in the present invention refers to a polyhydric alcohol with a valence of 3 or more, or a derivative thereof, (meth)acrylic acid, or these. A crosslinking monomer obtained by reacting an acid with a halide or ester, such as trimethylolpropane tri(meth)acrylate,
pentaglycerol tri(meth)acrylate,
Examples include pentaerythritol tetra(meth)acrylate. Such polyfunctional monomers are the main components that form a cross-linked cured film when irradiated with active energy rays, but some of them, when irradiated in air, undergo a cross-linking and curing reaction due to oxygen in the air. Some of them are suppressed and do not exhibit sufficient wear resistance. In such cases, it is necessary to perform the irradiation in an inert gas atmosphere such as nitrogen gas or carbon dioxide gas. Since this is disadvantageous in practice due to the complexity of the working process, it is more preferable to use a monomer that can form a crosslinked cured film having sufficient abrasion resistance by irradiation in the air in carrying out the present invention. A polyfunctional monomer that satisfies this condition has the following general formula: (In the formula, X ₁₁ , X ₁₂ , X ₁₃ , X ₂₂ , X ₂₃ ..., X _o2 ,
At least three of X _o3 and X ₁₄ are CH ₂ = CR−
The COO group and the rest are -OH groups. n is an integer from 2 to 5. R is hydrogen or a methyl group. ) Polypentaerythritol poly(meth)acrylate is mentioned. It has very good polymerization activity upon irradiation with active energy rays and is crosslinked and cured to form a polymer exhibiting a high degree of wear resistance. Specific examples include pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate,
Examples include dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and the like. Two or more of the above polyfunctional monomers can also be used in combination. If the amount of the polyfunctional monomer (a) is less than 30 parts by weight, the hardness and abrasion resistance of the cured film will be poor, or the recording film will be prone to mottling. Furthermore, if the amount exceeds 90 parts by weight, the adhesion to the synthetic resin board may become poor or the cured film may become more likely to become mottled. The mono- or di-functional monomer (b) can be copolymerized with the polyfunctional monomer (a), and examples of monomers having one (meth)acryloyloxy group per molecule include, for example, acrylic Examples include acids, methacrylic acid or esters thereof, acrylonitrile, styrene, and derivatives thereof. A monomer that is highly curable in air has at least one ether bond in one molecule and has a boiling point of 150 at normal pressure.
℃ or above and a viscosity of 20 centipoise or less at 20℃, specific examples include 2-ethoxyethyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, and phenoxyethyl (meth)acrylate. meth)acrylate, 2-(2-methoxyethoxy)-ethyl(meth)acrylate, 2-(2-ethoxyethoxy)-ethyl(meth)acrylate, tetrahydrofurfuryl(meth)acrylate, 2-tetrahydrofurfuryloxyethyl( meth)acrylate, 2-glycidyloxyethyl(meth)
Examples include acrylate. These are essential components from the viewpoint of in-air curability and coating film smoothness.
(meth)acryloyloxy group per molecule is 2
Examples of diethylenically unsaturated substances include glycol di(meth)acrylate, polyalkylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate. Examples include compounds. In addition, examples of compounds with high curability in air include the following general formula: (In the formula, X ₁ , X ₂ ...X _o1 is an alkylene group having 6 or less carbon atoms or one hydrogen atom thereof is substituted with a hydroxyl group, and n ₁ is an integer from 0 to 5) Specifically, 2,2-bis(4-
acryloyloxyphenyl)propane, 2,2
-bis(4-acryloyloxyethoxyphenyl)propane, 2,2-bis(4-acryloyloxydiethoxyphenyl)propane, 2,2-
Bis(4-acryloyloxypropoxyphenyl)propane, 2,2-bis[4-acryloyloxy(2-hydroxypropoxy)phenyl]
There are propane, etc. These are effective in imparting flexibility and adhesion to the resin plate to the cured film. Monomer mixture constituting the curing liquid composition of the present invention
The organic solvent (B) used in combination with (A) has extremely favorable effects on workability, uniform coating film formation, and storage stability when coating the coating composition on the surface of a synthetic resin board. It is also used to increase the adhesion of the crosslinked cured coating to the resin plate. The organic solvent used in the present invention (1) forms a homogeneous solution when mixed with the polyfunctional (meth)acrylate monomer mixture (A), and (2) has a boiling point of 50°C or higher at normal pressure. (3) The viscosity at room temperature is 10 centipoise or less. Specifically, alcohols such as ethanol, isopropanol, n-propanol, isobutyl alcohol, and n-butyl alcohol, aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene, ketones such as acetone and methyl ethyl ketone, and ethers such as dioxane. , ethyl acetate, n-butyl acetate, ethyl propionate, and other acid esters, N,N-dimethylformamide, and the like. One type of these organic solvents may be used alone, or two or more types may be used in combination as long as the boiling point and component ratio of the mixture are within the range that satisfies the above-mentioned requirements. To apply the curing liquid of the present invention to the surface of a synthetic resin board, any of the usual coating methods such as casting, spraying, rotation, and dipping can be applied, but especially uniform and smooth coating methods can be used. For substrates for information recording disks that require coating film formation, the dipping method and the rotation method are most suitable. The thickness of the coating film obtained by curing the above-mentioned curing liquid is selected depending on the recording and reproducing system used, but if it is too thick, cracks will occur and the smoothness will decrease, and if it is too thin, the hardness will decrease. Considering the depth of focus of the system, it is preferable to set the depth to be in the range of 1 to 30μ, preferably 3 to 10μ. Applying the curing liquid of the present invention to the surface of a synthetic resin board,
In order to form a crosslinked cured film, it is necessary to irradiate with active energy rays such as ultraviolet rays, electron beams, or radiation. Among these, the method using ultraviolet irradiation is the most preferred from a practical standpoint. When ultraviolet rays are used, the curing speed can be increased by adding a photosensitizer to the curing solution that initiates the polymerization reaction of monomers upon irradiation with ultraviolet rays. Specific examples of such photosensitizers include:
Carbonyl compounds such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, acetoin, butyroin, toluoin, benzyl, benzophenone, p-chlorobenzophenone, p-methoxybenzophenone, tetramethylthiuram monosulfide,
Sulfur compounds such as tetramethylthiuram disulfide, azobisisobutyronitrile, azobis-
Examples include azo compounds such as 2,4-dimethylvaleronitrile, and peroxide compounds such as benzoyl peroxide and di-t-butyl peroxide. These photosensitizers may be used alone or in combination of two or more. The appropriate amount of photosensitizer to be blended is 0.01 to 10 parts by weight per 100 parts by weight of the curing solution. For curing, irradiation with active energy rays is performed.
Implementation will be carried out in stages. In the first stage of preliminary irradiation, at least one side of the synthetic resin plate is only cured up to the half stage, a fluid molding resin is provided on the cured film of the half stage, a matrix is placed on top of the fluid molding resin, and A second stage of active energy rays is irradiated through the resin plate to simultaneously cure the cured film of the half stage and the fluid molding resin, thereby bringing the cured film layer and the information recording layer into close contact. The half-stage cured film in the present invention refers to a cured film with a pencil hardness of B to 4H, and completion of curing means that the pencil hardness of the cured film reaches a level of 6H or higher. Generally, the pencil hardness of a synthetic resin board is B to H, and the scratch resistance of a half-stage cured film is equivalent to or better than that of an untreated synthetic resin board. Adhesion between the information recording layer and the cured film layer becomes remarkable by such a two-stage irradiation method. To create such a half-stage cured film, it is possible to freely adjust the irradiation conditions of active energy rays, and the irradiation time, distance, and oxygen concentration can be adjusted as appropriate depending on the type of curing liquid and active energy rays used. etc. can be selected. Note that for cured surfaces that are not provided with fluid molding resin, the first stage may be used as a half stage and curing may be completed in the second stage.
If the first stage is a half stage, it is likely to be damaged in subsequent steps, so it is preferable to complete curing in the first stage. This is easily accomplished by varying the irradiation intensity on both sides of the irradiation. The method of the present invention described above is particularly effective when the curing liquid applied to the surface of the synthetic resin board is photopolymerizable. Even when the curing liquid is a thermosetting curing liquid, by forming a half-stage cured film based on the concept of the present invention, the adhesion with the information recording layer can be improved to some extent, but it is not sufficient. Furthermore, it is necessary to separately form the information recording layer and complete the curing of the half-stage cured film, which complicates the process, and also causes distortion and deformation of the synthetic resin plate due to heat treatment when curing is completed. There is a drawback that accuracy of recording and reproduction occurs. On the other hand, in the case of a photopolymerizable curing liquid, even if the curing is divided into two stages, the second stage of irradiation is performed at the same time as the formation of the information recording layer, which is an originally essential process, so there is no substantial increase in the number of steps and it is economical. It is true. It is also possible to use the above-mentioned curing liquid as it is as the fluid molding resin in the present invention. In particular, in order to fully exhibit the effects of the present invention, low molecular weight mono-, di-, tri- or tetra-(meth)acrylic acid
A radiation-curable compound containing a liquid mixture of esters is preferred from the viewpoint of adhesion to the synthetic resin plate. Specific examples include alkyl (meth)acrylate, phenyl (meth)acrylate, alkoxy (meth)acrylate, alkylene glycol di(meth)acrylate, polyalkylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, polyester. Examples include (meth)acrylate, urethane (meth)acrylate, and epoxy (meth)acrylate, and these may be used alone or as a mixture. When the above fluid molding resin is applied onto a synthetic resin plate in the usual manner, a matrix is applied, and active energy rays are irradiated through the synthetic resin plate, the fluid molding resin hardens and the recording signal on the surface of the matrix is transferred. Ru. As a method for applying the fluid molding resin, a rotation method is suitable from the viewpoint of the accuracy of the obtained film thickness. It is advantageous to remove the synthetic resin plate from which signals have been transferred, that is, to record information, from the matrix, and to further form a light-reflecting layer of aluminum or the like on its surface by vapor deposition. Further, if necessary, a suitable protective layer may be provided on the light reflecting layer, or the protective layers of two disks (information recording bodies) may be bonded together to be used as a set of disks. In this way, the outer layers on both sides of the information recording medium are protected by the scratch-resistant cured film, and the effects of the present invention are most effectively exhibited. The present invention can also be fully applied to an information recording medium in which information is reproduced using transmitted light, and in this case, it is preferable to form a scratch-resistant cured film using the curing liquid of the present invention instead of the light-reflecting layer. It's advantageous. Hereinafter, the present invention will be explained in more detail with reference to Examples. Examples 1 to 7 and Comparative Examples 1 to 6 1.5 mm thick methyl methacrylate resin plate (Acrylite L (registered trademark) manufactured by Mitsubishi Rayon Co., Ltd.
Cut out a 30cm disk and use it as a synthetic resin plate that will become the substrate of the information recording medium. Dip each resin plate into each curing liquid shown in Table 1 and apply the curing liquid to both sides of the resin plate. did. The resin plate was lifted from the curing solution, left for 1 minute, and then preliminarily irradiated with ultraviolet rays using a 2KW high-pressure mercury lamp under the predetermined conditions shown in Table 1 to form a cured film layer with a thickness of about 4μ. Next, a fluid molding resin consisting of 8 parts by weight of methyl methacrylate, 20 parts by weight of trimethylolpropane triacrylate, and 2 parts by weight of benzoin isobutyl ether was spin-coated on the surface of the cured film of the half stage (hereinafter referred to as side A), and on this Diameter 30cm
Apply the aluminum flat disc matrix,
Ultraviolet rays from the same light source as above were irradiated for 60 seconds from a distance of 20 cm from the cured film surface on the opposite side (hereinafter referred to as side B) to complete the formation of the information recording layer and the curing of side A at the same time. After removing the disk matrix, a light reflective layer of aluminum having a thickness of approximately 300 Å was provided on the cured fluid molding resin by vacuum deposition to produce a single-sided information recording medium. Various performance evaluation results are shown in Table 2 along with comparative examples. As is clear from the results in Table 2, the adhesion of the information recording layer is improved by the two-stage irradiation method using a half stage. In a system in which fluid molding resin is applied after curing is completed in the first stage (Comparative Example 2) or in a system in which the hardness of the first stage half stage is 4H or more (Comparative Examples 2 and 4), the information recording layer does not adhere tightly. The hardness of the substrate deteriorated and there were no foreign substances on the disk surface, and no significant improvement was observed compared to the substrate that was not hardened (Comparative Example 1). Further, even if the hardness of the half stage was 3H, which was within the conditions of the present invention, a system with an inappropriate curing liquid composition (Comparative Example 3) resulted in poor smoothness, adhesion, etc. On the other hand, it is confirmed that all of the samples manufactured under the conditions of the present invention exhibited excellent performance, and the number of surface foreign substances was greatly reduced. In addition, in order to cure to half stage, the method of increasing the irradiation distance (Examples 1, 2, and 6), the method of shortening the irradiation time (Example 4), and the method of increasing the oxygen concentration compared to Example 1 (Example 5) ), or a method of combining a monomer with low air curability and a monomer with high air curability (Example 7), etc. are effective. Also, a method in which both sides of the synthetic resin substrate are cured to a half stage in the first stage and curing is completed during exposure in the second stage (Examples 3, 5, and 7).
is also valid. Performance was evaluated using the following method. (1) Scratch resistance Pencil hardness was measured and compared according to JIS K5651-1966. (2) Adhesion Both the cured film layer and the information recording layer were evaluated by a cross-cut cellophane tape peel test. Cut 11 film cutting lines vertically and horizontally into the film at 1 mm intervals to create 100 ¹ mm squares, then press cellophane tape onto the film, then peel it off sharply in a 90 degree direction for comparison. It was evaluated by 〇 No number of flakes × Number of flakes: 1 to 50 pieces △ Number of flakes: 51 to 100 pieces (3) Surface foreign matter Observe the state of foreign matter on the disk surface with a microscope, and compare it with the case where a substrate without surface treatment is used as a standard. , evaluated based on the following criteria. Foreign substances significantly decreased + 〃 Slightly decreased 〃 〃 Almost unchanged - 〃 Slightly increased

【table】

【table】

Claims (1)

[Claims] 1 30 to 90 parts by weight of polyfunctional monomer (a) having 3 or more (meth)acryloyloxy groups per molecule and 1 to 1 to 1 to 2 (meth)acryloyloxy groups having 1 or 2 (meth)acryloyloxy groups per molecule Bifunctional monomer (b)10
5 to 90 parts by weight of a monomer mixture (A) consisting of ~70 parts by weight, and 95 to 10 parts by weight of at least one organic solvent (B) which is mixed with the mixture (A) to form a homogeneous solution. 0 to 10 parts by weight of photosensitizer (C) (the above mixture (A) and organic solvent (B)
A photopolymerizable curing liquid consisting of (based on a total of 100 parts by weight of forming a fluid molding resin on the cured film of the half stage;
The method is characterized in that the cured film of the half stage and the fluid molding resin are completely cured at the same time by placing a mother mold on the fluid molding resin and then irradiating active energy rays through the resin plate. A method for manufacturing an information recording medium.