JP2006018944A - Optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply and inexpensively provide an optical disk which can fully suppress deformation (warpage) accompanying change of temperature and humidity and is excellent in mechanical strength. <P>SOLUTION: The optical disk is equipped with a protective coat which is made up by polymerizing the ester modified (meta) acrylate resin which is made by carrying out esterification reaction to the (meta) acrylic acid, to a hydroxyl group-containing esterification material comprising photocuring silicone resin containing siloxane skeleton or 2 basic acid having carboxyl group to both ends of the alkylene chain of carbon numbers 1-6, and polyhydric alcohol. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical disk having a reflective film, a recording film, a protective film, etc. on a substrate, used as an optical information recording medium used in the field of video and sound, and in particular, recording / reproducing information with a blue-violet light source. The present invention relates to an optical disc.

  In recent years, development of an optical disc for Blu-ray as a next generation optical disc has been active. Currently, optical discs such as CDs and DVDs are already in widespread use, and there is a demand for higher density, higher capacity, and smaller size. In recent years, development aimed at high performance and high quality corresponding to HDTV is increasing, and today, there is a strong demand for improving the performance of each member constituting the disk. In particular, an optical disc for Blu-ray is required for a protective film because the recording / reproducing laser beam has a high aperture by increasing the density and the light input / output is applied to the recording / reproducing method from the protective film side. The characteristics are more severe than ever before.

  Conventionally, many photo-curing resins have been studied as such protective films. For example, improvements have been made to the constituent materials and improvements to react by adding many kinds of reaction initiators mixed in the resin. However, due to the lack of thickness, deterioration of film formability, and poor characteristics due to deformation caused by changes in temperature and humidity, satisfactory effects were not obtained and the performance was completely insufficient.

As a specific example, for example, a cured film obtained using a compound having two or more maleimide groups in a molecule has been proposed (see Patent Document 1).
Further, for example, a transparent substrate, a thin film layer formed on one surface of the transparent substrate, a thin film protective film formed on the thin film layer, and a substrate protective film formed on the other surface of the transparent substrate In an optical information recording medium equipped with the above, a technique for suppressing deformation (warpage) associated with a change in humidity by making the humidity expansion coefficient of the substrate protective film larger than the humidity expansion coefficient of the thin film protective film has been proposed. (See Patent Document 2). Further, it is described that the substrate protective film and the thin film protective film are formed of an ultraviolet curable resin mainly composed of polyester acrylate, epoxy acrylate, urethane acrylate, polyether acrylate, or the like.
Japanese Patent Laid-Open No. 2002-170281 (refer to the claims on page 2) JP 2002-298437 A (Page 3 Means for Solving the Problems)

However, in the technique of Patent Document 1, it is conceivable that the reactivity becomes short, but the action of reducing the shrinkage deformation cannot be expected from the structure of the maleimide compound.
Moreover, in the said patent document 2, since the physical property desire of each material with which each material with which it has provided on a member surface should be only mentioned, a characteristic changes greatly with what is used from the protective film material of description, Since humidity changes Deformation (warping) that accompanies sometimes is not always sufficiently suppressed.

  An object of the present invention is to provide an optical disc that can sufficiently suppress deformation (warpage) associated with temperature change and humidity change and that has excellent mechanical strength (surface hardness and scratch resistance) at low cost and simply. And

  The present invention relates to an optical disc comprising a protective film obtained by polymerizing a photocurable silicone resin containing a siloxane skeleton.

  The present invention also provides an ester modification (meta) obtained by esterifying (meth) acrylic acid to a hydroxyl group-containing esterified product of a dibasic acid having a carboxyl group at both ends of an alkylene chain having 1 to 6 carbon atoms and a polyhydric alcohol. The present invention relates to an optical disc comprising a protective film formed by polymerizing an acrylate resin.

  The optical disk of the present invention can sufficiently suppress deformation (warpage) associated with temperature change and humidity change, and is excellent in mechanical strength (surface hardness and scratch resistance). Further, since the protective film is obtained by polymerizing (curing) a specific silicone resin or ester-modified (meth) acrylate resin, the protective film can be provided inexpensively and easily. Furthermore, when a hard coat film is provided, the mechanical strength is further improved.

Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram of an optical disc according to an embodiment of the present invention.
As shown in FIG. 1, the optical disk of the present invention has a media layer 2 and a protective film 3 sequentially laminated on one side of a substrate 1.

  The substrate 1 can be used regardless of organic and inorganic materials as long as the transparency and flatness of the disk can be secured. For example, the base material may be made of polycarbonate resin, polyacrylic resin, glass or the like. From the viewpoint of more effectively preventing deformation associated with temperature change and humidity change, it is preferably made of polycarbonate resin. The thickness of the substrate is not particularly limited, but is preferably 1 to 1.1 mm.

  The media layer 2 may be made of any inorganic or organic material as long as it exhibits various functions such as reflection, recording, and dielectric, and may have a single layer structure or a multilayer structure. May be. For example, in the case of a layer that functions as a reflective film, the constituent material of the layer is typically a metal such as silver, gold, or aluminum. Usually, a recording film made of Ge alloy or a dielectric film made of Ta alloy is further formed on the reflective film to form the media layer 2. Here, only a representative media layer configuration is described, and the present invention is not limited to the above configuration, and any other configuration may be used. The media layer can be formed by a method such as sputtering.

  In the present invention, the protective film 3 is obtained by polymerizing (curing) a specific silicone resin or a specific ester-modified (meth) acrylate resin.

The silicone resin that can form the protective film 3 is a photocurable silicone resin containing a siloxane skeleton, and one or more selected from the group consisting of vinyl groups, acrylic groups, acrylonitrile groups, and epoxy groups in the molecule. These have at least one reactive group.
In this specification, an acrylic group is used in a concept including a (meth) acryloyl group and a (meth) acryloyloxy group. The (meth) acryloyl group is used in a concept including an acryloyl group and a methacryloyl group. For example, (meth) acrylate is meant to include acrylate and methacrylate. Accordingly, the acrylic group specifically includes CH ₂ ═CH—CO—, CH ₃ CH═CH—CO—, CH ₂ ═CH—CO—O—, and CH ₃ CH═CH—CO—O—.
The acrylonitrile group is represented by CNCH═CH—.
In addition, the epoxy group is used in a concept including not only a monovalent residue obtained by removing hydrogen from ethylene oxide but also a glycidyl group and a glycidyloxy group.

  Since the siloxane skeleton has a —Si—O— structure, the element bond interval is longer and the bond angle is larger than the —C—C— and —C—O— structures found in general carbon-based polymers. Therefore, the siloxane skeleton has a large degree of freedom in the molecule and is rich in molecular stretchability. Therefore, silicone resin molecules have a tolerable range of change with respect to shrinkage and expansion compared to carbon-based monomers such as acrylic monomers, even with the generation of desorbed molecules and the incorporation of heat and moisture into the film. It is considered that the deformation (warp) is small because it is wide based on the length between them and the large coupling angle.

で表される。 Specifically, the silicone resin used in the present invention is represented by the general formula (I);

It is represented by

In the formula (I), at least one R out of all R is a group containing the above reactive group (hereinafter simply referred to as a reactive group-containing group).
The reactive group-containing group is not particularly limited as long as it contains at least a part of the reactive group, and examples thereof include a vinyl group, an acrylic group, an acrylonitrile group, an epoxy group, and one or a group selected from these groups Examples include a composite group in which a further group is substituted with an alkyl group having 1 to 3 carbon atoms (for example, methyl group, ethyl group, n-propyl group, isopropyl group). Preferably, it is a composite group obtained by substituting one reactive group, particularly an epoxy group, with a branched alkyl group such as isopropyl.

The preferred number of reactive group-containing groups possessed by the silicone resin is not particularly limited as long as the object of the present invention is achieved, but it varies depending on the type of reactive group from the viewpoint of easy availability of the silicone resin.
For example, when the reactive group is a vinyl group, an acryl group or an acrylonitrile group, the number of the reactive group-containing groups is 1 or more, preferably 1 to 3, and more preferably 2 to 3.
For example, when the reactive group is an epoxy group, the number of reactive group-containing groups is preferably 1 to 3, particularly preferably 2 to 3.

When the silicone resin has two or more reactive group-containing groups, the reactive group-containing group may be independently selected from the above range.
Further, when the silicone resin has two or more reactive group-containing groups, the two reactive group-containing groups are preferably substituted at both ends of the siloxane skeleton, and at this time, other reactive group-containing groups The substitution position is not particularly limited.

In the formula (I), the other Rs are each independently a group not containing the reactive group (hereinafter referred to as a reactive group-free substituent).
Examples of the reactive group-free substituent include a hydrogen atom, an alkyl group, and an aryl group. The alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, particularly 1, and examples thereof include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. The aryl group preferably has 6 to 10 carbon atoms, particularly 6 carbon atoms, and examples thereof include a phenyl group and a naphthyl group. Preferred are bulky groups such as aryl groups, especially phenyl groups.

  k is not particularly limited as long as the object of the present invention is achieved, and is preferably 100 to 700, particularly preferably 400 to 600.

  The molecular weight of the silicone resin is such a value that k is within the above range. Usually, the ease of film formation, the kind and amount of reaction initiator, the speed of curing, and the surface to be obtained Hardness (pencil test) can be achieved. In addition to ease of availability and price, considering the fact that it is not restricted by laws and regulations such as harmfulness and disposal, silicone resins having different molecular weights may be mixed and used.

  The silicone resins as described above are available as commercially available TUV6001, XR39-C1132 (above, manufactured by GE Toshiba Silicone), X-40-2670, X-40-2686 (above, manufactured by Shin-Etsu Chemical Co., Ltd.), and the like. .

  A protective film made of a silicone resin can be formed by applying a mixture of a silicone resin and a reaction initiator on a media layer by a known coating method such as a spin coating method, and sufficiently irradiating with ultraviolet rays and curing. The light source is not particularly limited, and a metal halide lamp or the like can be used.

  As the reaction initiator, when the silicone resin has a reactive group-containing group containing a vinyl group, an acrylic group or an acrylonitrile group as a reactive group, a radical reaction initiator is used. By using a radical reaction initiator, the addition reaction by the unsaturated double bond of the said reactive group occurs, coupling | bonding of reactive group occurs, As a result, superposition | polymerization of a silicone resin advances.

As the radical reaction initiator, those conventionally used as a photoreaction initiator can be used, and examples thereof include phenyl ketones, phosphine oxides, aminobenzoates, and thioxanthones.
Specific examples of phenyl ketones include anthraquinone, benzophenone, acetophenone, and the like.
Specific examples of phosphine oxides include 2,4,6-trimethylbenzoyldiphenylphosphine oxide.
Specific examples of aminobenzoates include 2-benzyl 2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 and the like.
Specific examples of thioxanthones include 2,4-diethylthioxatone.

  Among the radical reaction initiators, phenyl ketones, phosphine oxides and aminobenzoates are preferable, and phenyl ketones, particularly anthraquinone or benzophenone are more preferable. This is because a protective film (cured film) can be formed at a low cost and at a high speed.

  When the silicone resin has a reactive group-containing group containing an epoxy group as a reactive group, an ion cleaving agent is used as a reaction initiator. By using an ion-cleaving agent, an addition reaction due to the ring opening of the epoxy ring occurs and the epoxy groups are linked to each other. As a result, the polymerization of the silicone resin proceeds.

  As the ion-cleaving agent, those conventionally used as an ion-cleaving agent for epoxy rings can be used. For example, Lewis acid allyldiazonium salt, diallyliodonium salt and the like can be used. When an allyldiazonium salt of Lewis acid is used, a film is formed during the curing process of the cation reaction, and a hard film can be obtained quickly. In addition, since the polymerization process is an ionic reaction, there is no reaction inhibition by oxygen, and complete curing proceeds even if left alone, so that there is no fear of uncured.

The Lewis acid allyldiazonium salt generates a Lewis acid and contains any one of Sb, Sn or Fe and I and F. For example, the general formula:
[R (C ₆ H ₄ )] ₂ ISbF ₆
(Wherein, R represents a monovalent hydrocarbon group having 10 to 14 carbon atoms, particularly an alkyl group). When such a compound is used to polymerize a silicone resin having three epoxy groups in the molecule, a protective film with improved mechanical strength can be obtained.

  The content of the reaction initiator is not particularly limited, and is preferably 1 to 4% by weight, particularly 2 to 3% by weight, based on the total amount of the silicone resin mixture to be applied.

The ester-modified (meth) acrylate resin capable of forming the protective film 3 is obtained by esterifying (meth) acrylic acid with a hydroxyl group-containing esterified product of a dibasic acid and a polyhydric alcohol. A dibasic acid has a carboxyl group at both ends of an alkylene chain, and in the present invention, the carbon number of the alkylene chain is adjusted to improve the molecular stretchability of the ester-modified (meth) acrylate resin. The number of carbon atoms in such an alkylene chain is selected not only from the viewpoint of molecular stretchability, but also from the viewpoint of an appropriate balance between the protective film surface hardness and the resin molecule hydrophobicity. That is, from the viewpoint of the surface hardness of the protective film, the number of carbon atoms in the alkylene chain is preferably small. As a result, the molecular stretchability becomes low, and deformation due to temperature change and humidity change cannot be sufficiently suppressed. On the other hand, if the number of carbon atoms in the alkylene chain is too small, the hydrophobicity of the resin molecules becomes small, and uniform coating during the production of the protective film becomes difficult. Therefore, in order to increase the hydrophobicity of the resin molecule, it is necessary to increase the carbon number of the alkylene chain to some extent. However, if the number of carbon atoms in the alkylene chain is too large, the molecular stretchability becomes too large, and an adverse effect occurs on the warp of the film, exceeding the standard value. Also, the desired surface hardness cannot be obtained. Therefore, the carbon number of the alkylene chain is determined in consideration of the balance of molecular stretchability, protective film surface hardness, and resin molecule hydrophobicity, and specifically, 1 to 6 is preferable.
The polyhydric alcohol is a divalent to tetravalent saturated aliphatic alcohol. The number of carbon atoms of the polyhydric alcohol is not particularly limited as long as the object of the present invention is achieved, but 3 to 6 is preferable from the viewpoint of the molecular stretchability of the resin molecule.

で表されるものが挙げられる。 As a preferable specific example of such ester-modified (meth) acrylate resin, general formula (II);

The thing represented by is mentioned.

In the formula (II), R ¹ and R ⁵ are each independently a hydrogen atom or a methyl group.
R ² and R ⁴ are each independently an alkylene group having 3 to 6 carbon atoms, particularly 4 to 5 carbon atoms, and may be linear or branched. For example, a trimethylene group, a propylene group, etc. are mentioned. R ² and R ⁴ may have a substituent such as a hydroxyl group, and may further have an ether form in which the alkylene group is linked via an oxygen atom. Specific examples of the compound molecule that can derive R ² and R ⁴ include dipropylene glycol, 1,2-propylene glycol, and the like. In these compound molecules, R ² and R ⁴ are derived by removing any two hydrogen atoms, particularly hydrogen atoms possessed by a carbon atom having a hydroxyl group.
R ³ is a linear alkylene group having 1 to 6 carbon atoms, particularly 3 to 5 carbon atoms. Specific examples of such R ³ include a trimethylene group.
m is a value such that the viscosity of the resin falls within the range described below.

  The molecular weight of the ester-modified (meth) acrylate resin is within a range such that the viscosity of the resin alone is 700 to 3500 mPa · s, particularly 800 to 2500 mPa · s. By using a resin that achieves such a viscosity, the object of the present invention can be effectively achieved, and handling during application of the resin mixture, availability of the resin, and manufacturing cost are improved.

  As the viscosity of the solution, a value measured by a B-type viscometer (rotor type) (TYPE TV-10; manufactured by Toki Sangyo Co., Ltd.) at 25 ° C. is used. However, it does not have to be measured by the viscometer, and may be measured by any viscometer as long as it can measure the solution viscosity at the temperature.

Such ester-modified (meth) acrylate resins as described above are available as commercially available UVPC-001-03, UVPC-001-07, UVPC-001-05 (above, Nippon Kasei Co., Ltd.) and the like.
In the present invention, two or more kinds of ester-modified (meth) acrylate resins may be mixed and used.

  The protective film made of an ester-modified (meth) acrylate resin is a protective film made of the above-mentioned silicone resin except that the above-mentioned ester-modified (meth) acrylate resin is used instead of the silicone resin, and the radical reaction initiator is used as a reaction initiator. The film can be formed by a method similar to the film forming method. By performing ultraviolet irradiation using a predetermined material, an addition reaction due to an unsaturated double bond of the (meth) acrylate moiety in the ester-modified (meth) acrylate resin occurs, and the (meth) acrylate moiety is linked between molecules. Occurs, and as a result, polymerization of the ester-modified (meth) acrylate resin proceeds.

  Preferred radical reaction initiators are phenyl ketones and thioxanthones, more preferably phenyl ketones, particularly benzophenone and acetophenone. This is because it is easily available and inexpensive.

  The content of the reaction initiator is not particularly limited, and is preferably 1 to 5% by weight, particularly preferably 2 to 3% by weight, based on the total amount of the ester-modified (meth) acrylate resin mixture to be applied.

From the viewpoint of improving the handling of the mixture, a reaction diluent may be further mixed into the mixture of the ester-modified (meth) acrylate resin and the reaction initiator used when forming the protective film.
The reaction diluent is not particularly limited as long as it is a compound that can dissolve the ester-modified (meth) acrylate resin, and examples thereof include acrylates such as 2-ethylhexyl, 1,6-hexanediol, and trimethylol. Can be mentioned.

  The content of the reaction diluent is not particularly limited, and is preferably 5 to 40% by weight, particularly 5 to 20% by weight, based on the total amount of the ester-modified (meth) acrylate resin mixture to be applied.

The surface hardness of the protective film formed from the silicone resin or ester-modified (meth) acrylate resin as described above is H or higher, preferably 3H or higher, in terms of pencil hardness.
The thickness of the protective film is not particularly limited as long as the object of the present invention can be achieved without impeding the function of the optical disk, and is preferably 98 to 102 μm, for example. In addition, when further forming a hard coat film which will be described in detail later, the total thickness thereof is preferably within the above range.

  In another embodiment of the present invention, an optical disk has a hard coat film on the protective film 3 of the optical disk shown in the above embodiment. By forming the hard coat film, the surface mechanical strength (surface hardness and scratch resistance) is more effectively improved. This is particularly effective when laser light irradiation for recording / reproduction is performed from the protective film surface.

  The hard coat film includes inorganic fine particles contained and dispersed in a polymer (cured product) of the above-described silicone resin or ester-modified (meth) acrylate resin.

  The hard coat film can be formed by a method similar to the method for forming the protective film, except that the inorganic fine particles are dispersed in the resin mixture.

  As the inorganic fine particles, for example, silica, ammonium paramolybdate, whisker, and a mixture thereof can be used. From the viewpoint of production cost, silica, particularly colloidal silica is preferred.

  The average primary particle size of the inorganic fine particles is not particularly limited as long as it is less than ½ of the wavelength of the laser beam for recording / reproducing, and is usually 10 to 100 nm, preferably 10 to 50 nm.

  The content of the inorganic fine particles is not particularly limited, and is preferably 5 to 40% by weight, particularly 5 to 20% by weight, based on the total amount of the hard coat film forming resin mixture to be applied.

  The resin used for forming the hard coat film is preferably the same type of resin as used for forming the protective film from the viewpoint of adhesion to the protective film. That is, for example, when the protective film is formed from the silicone resin, the hard coat film is also preferably formed from a resin selected from the range of the silicone resin. For example, when the protective film is formed from the ester-modified (meth) acrylate resin, the hard coat film is also preferably formed from a resin selected from the range of the ester-modified (meth) acrylate resin. .

The resin for forming a hard coat film is available as a commercially available resin mixture that contains inorganic fine particles in advance.
For example, a resin mixture of silicone resin and silica is available as commercially available UVHC-1101 (manufactured by Toshiba GE Silicone), X-41-2420B, X-41-2420C (above, Shin-Etsu Chemical Co., Ltd.).
Further, for example, a resin mixture of an ester-modified (meth) acrylate resin and silica is available as commercially available UVPC-001, UVS-001 (manufactured by Nippon Kasei Co., Ltd.) or the like.

  The thickness of the hard coat film is preferably a value such that the total thickness with the protective film is particularly 98 to 102 μm from the viewpoint of improving the tear resistance. The thickness of the hard coat film alone is usually 0.5 to 6 μm, particularly preferably 0.5 to 1 μm.

  The surface hardness of the hard coat film is 2H or more, preferably 3H or more in terms of pencil hardness.

In the above embodiment, the optical disc has a configuration in which the media layer 2 and the protective film 3 and, if desired, a hard coat film (not shown) are sequentially formed on one surface of the substrate 1. It is not limited to this.
That is, in another embodiment of the present invention, the optical disc has not only a media layer and a protective film on one side of the substrate and a hard coat film if desired, but also one of the protective film or the hard coat film on the other side. Or you may have the structure by which both are formed. At this time, a media layer may be formed between the other surface and the protective film or the hard coat film. The substrate, media layer, protective film and hard coat film in such an embodiment are the same as those in the above embodiment.

(Experimental example 1)
Diameter 120 mm, was used polycarbonate plate having a thickness of 1 mm ^t. On one surface, a plurality of grooves of lands and grooves are formed on the surface, and a substrate on which a reflective film made of silver having a thickness of 20 nm is formed by sputtering is used as a base material. Next, a protective film was formed on the upper surface with the material structure shown in Table 1. Sample No. is as shown in Table 1.
The breakdown of the protective film components is the radical reaction type sample No. 1, 2, ion reaction type is sample No. Samples were made using 3 and 4, respectively, using a silicone resin and a reaction initiator. An acrylate resin was used as the main material of Comparative Sample 1.

  Specifically, the mixture of the main material and the reaction initiator is applied by spin coating at a temperature of 23 ° C. and a humidity of 50% RH so that the thickness after curing is 100 μm (Keyence's Proface rotary thickness meter). Then, it was photocured to form a protective film. In curing, a metal halide lamp was used as a light source and irradiation was sufficiently performed.

  The warpage was compared in the deformed state before and after the test 24 hours after each sample was placed in a thermostatic chamber rising to 60 ° C. and taken out after 80 minutes. For the measurement of the deformation state, the warpage of the disk (Dr. Shenk gubh, Pro meteus MT-136E) was obtained, the initial value of the comparative sample 1 was converted into a numerical value, and the values before and after the test were compared. The results are shown in FIG.

In Comparative Sample 1 formed of a general urethane product of acrylate, the warpage was large, such as being deformed to 1.5 after the sample test by the temperature test.
However, No. 1 provided with the protective film of the present invention. Although each sample of 1-4 had a characteristic difference in each, all became close to +/- 0.5, the small stress which acts on a base material appeared, and curvature was suppressed. These samples are considered to have been able to follow the deformation of the substrate because of the large spacing between silicon atoms and oxygen atoms and the intermolecular angle.

Moreover, in order to investigate the curvature by humidity, these were thrown in for 25 days under 25 degreeC and 90% RH, and after taking out, the curvature angle according to time was investigated. The results are shown in FIG. All of Samples 1 to 4 were more effective than Comparative Sample 1.
Therefore, in the base material having a film formed of the silicone resin of the present invention as a protective film, it is possible to provide a disk with very small sag due to heating and humidity.

(Experimental example 2)
A protective film was formed on the substrate in the same manner as in Experimental Example 1 except that the materials shown in Table 2 were used. The carbon number of the alkylene chain of the dibasic acid in the ester portion of the main material and the viscosity at 25 ° C. of the main material are shown in Table 2.

  The change in warpage before and after the temperature test and the change over time in the warpage after the humidity test were measured in the same manner as in Experimental Example 1. The results are shown in FIGS. 3 (A) and (B). In the temperature test result, the initial value of the comparative sample 2 is used as a standard. According to FIG. 3 (B), it was found that the comparative sample 2 originally had a large shrinkage, or the base material was greatly expanded due to the release of water, and expanded 8 times after 8 hours. In contrast, sample no. In Nos. 5 to 7, it was found that the warp angle had already reached saturation at 0.5 to 0.75 after 3 hours, and humidity deformation was greatly suppressed. From this, it can be seen that even an ester acrylate has a material configuration that can be actually used by devising the number of carbon atoms.

(Experimental example 3)
A protective film having a predetermined thickness was formed on the substrate in the same manner as in Experimental Example 1 except that the protective film material shown in Table 3 was used. Further, a hard coat film having a predetermined thickness was formed on the protective film in the same manner as in Experimental Example 1 except that the hard coat film material shown in Table 3 was used.

The change in warpage before and after the temperature test and the change over time in the warpage after the humidity test were measured in the same manner as in Experimental Example 1. Table 4 shows the warp angle after the temperature test and the warp angle after 7 hours of the humidity test.
The surface hardness was evaluated by pencil hardness. The surface strength was evaluated by the number of scratches generated by the Taber test.

  In addition to the large warpage, the comparative sample was not strong, such as scratches occurring twice, despite its surface hardness. This is presumably because the surface is composed only of polymer components. In contrast, sample no. In 8-12, it turns out that a deformation | transformation is small also with respect to a temperature and humidity change, and is suppressed. Moreover, since the powder was contained, even if the surface was small in hardness, the strength was more than three times that of the comparison. For this reason, the present invention can provide a disc that is less deformed and that guarantees stable recording and reproduction characteristics.

  The optical disc provided with the protective film of the present invention can be expected to have sufficient performance as a Blu-ray optical disc for recording and reproduction by light irradiation from the protective film side. Since these are high in density, they can be used as media for every aspect of consumer and business such as DVD, HDTV and computer memory.

1 shows a schematic cross-sectional view of an optical disc according to an embodiment of the present invention. (A) is a graph which shows the result of the temperature test performed in Experimental example 1, (B) is a graph which shows the result of the humidity test performed in Experimental example 1. FIG. (A) is a graph which shows the result of the temperature test performed in Experimental example 2, (B) is a graph which shows the result of the humidity test performed in Experimental example 2.

Explanation of symbols

1: base material, 2: media layer, 3: protective film.

Claims (11)

  An optical disc comprising a protective film obtained by polymerizing a photocurable silicone resin containing a siloxane skeleton.   A silicone resin containing a siloxane skeleton and having at least one group selected from the group consisting of a vinyl group, an acrylic group, an acrylonitrile group and an epoxy group in the molecule is polymerized with a reaction initiator. The optical disk according to claim 1, further comprising a protective film.   The silicone resin has at least one group selected from the group consisting of a vinyl group, an acrylic group and an acrylonitrile group in the molecule, and the reaction initiator is a phenyl ketone. Item 3. The optical disk according to Item 2.   The silicone resin has 1 to 3 epoxy groups in the molecule, the reaction initiator generates a Lewis acid, and is a Lewis acid allyldiazonium salt containing any one of Sb, Sn or Fe and I and F. The optical disk according to claim 2. The silicone resin has 3 epoxy groups in the molecule and the reaction initiator is of the general formula;
[R (C ₆ H ₄ )] ₂ ISbF ₆
The optical disk according to claim 2, wherein the optical disk is a compound represented by the formula: wherein R is a monovalent hydrocarbon group having 10 to 14 carbon atoms.   Polymerize ester-modified (meth) acrylate resin formed by esterification reaction of (meth) acrylic acid with a hydroxyl group-containing esterified product of a dibasic acid having a carboxyl group at both ends of an alkylene chain having 1 to 6 carbon atoms and a polyhydric alcohol An optical disc comprising a protective film formed by the method.   The optical disk according to claim 6, wherein the polyhydric alcohol is a divalent to tetravalent aliphatic alcohol having 3 to 6 carbon atoms.   (Meth) acrylic acid is esterified to a photocurable silicone resin containing a siloxane skeleton, or a hydroxyl group-containing esterified product of a dibasic acid having a carboxyl group at both ends of an alkylene chain having 1 to 6 carbon atoms and a polyhydric alcohol The hard coat film in which inorganic fine particles are contained in the polymer of the ester-modified (meth) acrylate resin formed as described above is further provided on the protective film. optical disk.   The optical disk according to claim 8, wherein the inorganic fine particles are one or more fine particles selected from the group consisting of silica, ammonium paramolybdate, and whiskers.   10. The optical disk according to claim 8, wherein the average primary particle diameter of the inorganic fine particles is 10 to 100 nm. 11. The optical disk according to claim 8, wherein the total thickness of the protective film and the hard coat film is 98 to 102 [mu] m.

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